Why do girls stick their hand down the back of a boy pants?

Answer 1

they either want the boy to do the same to them or they are just scared to put it in the front of the boys pants....

This sounds like something pre-teen girls might do. They don't know how to get a guy's attention so they do something silly like that. My neighbor did that to a boy in fifth grade and he was so startled that jumped away leaving my neighbor holding on to his ripped shorts and part of his undershorts. She was grounded for a month and he was embarrassed for the rest of the school year because most of the girls saw his bare bottom. Be aware of what you are doing, things can get out of control rapidly.

If this is an older teen doing this to a guy, it would usually mean she wants to get more physical with him. It also makes a difference if she is touching his underwear or bare bottom under his pants. If the guy likes the attention, go for it and return the favor. If not, tell her you are not interested in her and to knock it off.