Why don't people just make up their own religion?

[MilesTailsPrower]

A big reason people don't create their own religion is because a large chunk of theists automatically believe what their parents believed in. Religion is passed down from generation to generation like bad genetics and the cycle isn't broken until someone dares question the garbage they are fed. Considering religions like Christianity have the fear element, most people are afraid to even think outside the box out of the lingering belief that god might roast their soul on an open fire if they do.

I was talking to my extremist christian friend, I asked him if he was a "free-thinker" he said yes without knowing what it even meant. Then I told him a "free-thinker" is a atheist and states a load of shit out of the bible about if you deny me in front of your friends and I will deny you in front of my father, then he went on to say that he never said it and the bible never said it. God didn't strike him down with lightning but it sounds like religion is only real to you when it suits you best?