Why do people think and believe that it’s better to be with people who are the same gender as you rather than the opposite gender?

If you mean in a relationship, it's just about preference. If you're referring to friendship, it's also about preference, but also because they're usually more relatable and more likely to share the majority of your interests therefore easier to get along with. 

I don't want to be with beggars unless I want to **** them. You put a prepubescent child next to beggars and there's a 50/50 chance she will get molested. No thanks.

Beggars and biiitches :) (Adams and Eves)...BOOOOOOOOOORING

Put a gamble on it biiitches....