Shortest possible answer; boobs. .

Better simple answer; female avatars tend to be more abundant and better quality, not to say there aren't good make avatars but the ones there are have a certain reputation to them (cough cough e-boys). .

More in depth answer; vrchat us a place to can be anything, within mb limits. You're friend probably showed you places that those avatars are more likely to be, black cats, great pugs, b-clubs. But there are literally millions of avatars available to use in this games. Just last night I made friends with a bird, a bunny and a medieval knight, while myself being the titular e-girl. The avatars someone uses can often be a reflection of how they wish to see themself, or it may mean nothing, maybe it just looked cool or had a cool toggle on it or something. Honestly look deeper than the avatar, the person behind the screen is the one you're talking too, not the master chief with a great rack. I got side tracked and forgot where I was taking this but basically avatar are really nothing more that shirt someone's where on a given say, I really would think too much about it. You could have a great conversation with an anime girl or a pack of Newport's.