Why do some people think that being is a choice?

You've explained it very well. It's illogical to think someone would choose to be gay for all the reasons you have mentioned. Besides that, it's instinctual for gay people to be attracted to the same . That's simply the truth. So it would be illogical for someone to deny their instinctual orientation just to conform - sadly many do, and end up miserable. People who think ual orientation is a choice are simply close minded. It's not a choice - it's an inherent part of who one is.