well it hasn't...so why don't the christians change??!!
I apologize if this has been stated already
I'll assume you meant to say "He hasn't".
And He HAS revealed Himself. Some people simply refuse to see it. And it's all for a lack of effort. The Bible tells us that God will reveal Himself to those who diligently seek Him.
Diligent:
adjective
1.
constant in effort to accomplish something; attentive and persistent in doing anything:
a diligent student.
2.
done or pursued with persevering attention; painstaking:
a diligent search of the files.
In other words, you must want to know God with all your heart. Nothing less will suffice. Something is holding you back. If you truly want to know God, then YOU must make an effort. If you do not know God, then the problem lies with YOU. Not God.