I imagine breasts are considered sexual because the majority of people admiring them do so for sexual reasons. I rather suspect the people going 'MOMMY MILKERS' every time a busty female character shows up on screen are not doing so because they're tastefully admiring the female form. I also think the alleged double standard of men exposing their bare chests is balanced out by pretty much every game - even many of those rated for adults - refusing to depict authentic male anatomy. Just look at how few games have an option for a tasteful bulge or body hair but will spend a lot of time making sure that the female models look near perfect and appealing from every possible angle.