Just a simple question, why do people not believe in Christianity(an obvious truth to most of us)?

The bible gives the best answer: The Gospel is foolishness and a stumbling block.

Romans Paul is talking about the law and Israel, and how the gospel is an offense to it.

To be come a Christian they have to change their belief that the law and sacrifice has already been fulfilled through Christ. Which mean what they have believed and raised up on is now fulfilled. Thus changing their lifestyle and what it means to be a Jew.

1Co 1:17 For Christ did not send me to baptize, but to preach the gospel; not in wisdom of words, lest the cross of Christ should be made of no effect.
1Co 1:18 For the preaching of the cross is foolishness to those being lost, but to us being saved, it is the power of God.
1Co 1:19 For it is written, "I will destroy the wisdom of the wise, and I will set aside the understanding of the perceiving ones."
1Co 1:20 Where is the wise? Where is the scribe? Where is the lawyer of this world? Has not God made foolish the wisdom of this world?
1Co 1:21 For since, in the wisdom of God, the world by wisdom did not know God, it pleased God by the foolishness of preaching to save those who believe.
1Co 1:22 For the Jews ask for a sign, and the Greeks seek after wisdom;
1Co 1:23 but we preach Christ crucified, to the Jews a stumbling block, and to the Greeks foolishness.
1Co 1:24 But to them, the called-out ones, both Jews and Greeks, Christ is the power of God and the wisdom of God.
1Co 1:25 Because the foolish thing of God is wiser than men, and the weak thing of God is stronger than men.
1Co 1:26 For you see your calling, brothers, that not many wise men according to the flesh are called, not many mighty, not many noble.
1Co 1:27 But God has chosen the foolish things of the world to confound the wise; and God has chosen the weak things of the world to confound the things which are mighty;
1Co 1:28 and God has chosen the base things of the world, and things which are despised, and things which are not, in order to bring to nothing things that are;
1Co 1:29 so that no flesh should glory in His presence.

They're eyes have not been opened.

Well from the people Ive talked to...
It falls into a if there is a God why does he allow this to happen mentality.
Thats the most popular amongst my friends haha.

They are sinners who love their sin.

And Christianity is a contradiction to life itself. It renders every meaning of it made my man utterly worthless.

They believe there is a God. They just refuse to glorify Him.

But they're wasting their time refusing it, because God will be glorified through them in the end. Whether through their salvation or through their destruction is yet to be seen.

If I was brought up Buddhist, I wouldn't be a Christian.
With that scenario, I'd probably view Christianity as I do Buddhism today.
With my mindset, there's nothing a Buddhist could say to me to make me "convert".

I couldn't help but think, getting caught in that "if" - if I was Buddhist, I'd be screwed.

Then again, it is my core belief that God doesn't deny those who truly seek him.
Those who're putting for the effort - we're all doing the best that we can with what we got.

Religion isn't a requirement - all the laws, rules, traditions, rituals, traditions.... when the big picture is looked at, don't have a whole lot to do with the free gift of salvation or spirituality.

...and I can say that there's probably be millions of people that would pitch a loaf if they got to heaven, and God says, "Eh... You can call me Allah if you want."

Actually, that wouldn't surprise me one bit if He said that. (Even if it was His sense of humor)

Some people could call him Allah bro. Allah is Arabic for God.

Contrary to popular belief, Allah does not necessarily equal Islam. It all depends on who you're talking to.

My brother was brought up a Christian... is not one today... you actually have to choose to have faith.. if you do not.. its not real or tangible to you.

So you seek to fill those holes with many other things. We are told to look after numero uno, get a good job, sleep with whomever to show love, have an awesome house, good car and life will be good.

So we believe in life and ourselves when we get good things.

My bro is now looking at Taoism and The secret... even though He was around "christians" he didn't have his own faith or see enough of what he craved I guess... which was realness.

So I think some people want to believe in something, but look down some alleys they think is right for them... when perhaps it is not.

Ps( grew up going to a methodist then church of christ.. both legalistic and effed up)

People don't believe for a simple reason: they do not want to be held accountable and do not want to depend on anyone or anything besides themselves, because doing so will make them feel weak.

1 corinth.2:6We do, however, speak a message of wisdom among the mature, but not the wisdom of this age or of the rulers of this age, who are coming to nothing. 7No, we speak of God's secret wisdom, a wisdom that has been hidden and that God destined for our glory before time began. 8None of the rulers of this age understood it, for if they had, they would not have crucified the Lord of glory. 9However, as it is written:
"No eye has seen,
no ear has heard,
no mind has conceived
what God has prepared for those who love him"[b]— 10but God has revealed it to us by his Spirit.
The Spirit searches all things, even the deep things of God. 11For who among men knows the thoughts of a man except the man's spirit within him? In the same way no one knows the thoughts of God except the Spirit of God. 12We have not received the spirit of the world but the Spirit who is from God, that we may understand what God has freely given us. 13This is what we speak, not in words taught us by human wisdom but in words taught by the Spirit, expressing spiritual truths in spiritual words.[c] 14The man without the Spirit does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritually discerned. 15The spiritual man makes judgments about all things, but he himself is not subject to any man's judgment:
16"For who has known the mind of the Lord
that he may instruct him?"[d] But we have the mind of Christ.

i wrote a small article on this once.

Give me a reason to believe.

People dont believe because people wanna do what they wanna do with zero consequence,.... People have Just enough christianity to send them straight to Hell while they live comfortably and oblivious to the damnation to come...

OR they are complete atheist's who believe what "intelligent" free thinkers and Scientist's tell them about Evolution.