Sport?
I think you mixed up WITH and FOR.
Because they think they are more "fun"
If guys make fun of your good looking legs they are probably jealous that the girls like them.
because they think that girls are just for fun.
Guys may make fun of another guys legs because they are jealous.
because most guys think that it impresses girls or they don't think that they are showing off they are just having fun
Maybe guys don't make fun of a guy's arms because there is nothing to make fun of.
A guy may make fun of another persons legs because they like them.
Guys may make fun of other guy's legs because they are jealous.
no
Because they think there is a reason and they are guys and they know it bothers you. If it didn't it would take the fun out of it for them. Be happy they couldn't find anything better or you would be in for even worse ribbing.
As they are Fun guys (Fun-gis)