why many boys joined with girl profiles in dating site

Well maybe they are only looking to date themselves.

Way back in the 90's when I first started joining dating "sites" (chat rooms, message boards) I would sometimes start a girls profile.
I wanted to screw around and mess with people.
I wanted to know if lesbians were as filthy in their approach as some girls were reporting some guys were.
I wanted to know what other guys were privately sending to girls and measure it against what I was sending or get ideas.
I was starting college and wanted to pretend I was doing "social experiments" and that it would lead to greater information or secrets.

Now, I would imagine a lot of boys are joining with girl profiles in dating sites because they are scammers and also have other profiles that are male profiles.
Why leave out half the market?