You don't need to. Most bookstores, without any gender in their title, carry mostly books written by and about men. It's the same reason there's no "White Entertainment Television"; regular television is almost exclusively concerned with representations of white people. This is the Hierarchical Binary at play--whenever you've got two groups, and one group is on top and the other is on bottom, any neutral situation is assumed to be concerned with the group on top. This is one of the ways in which power structures are maintained insidiously; because this sort of discrimination isn't obvious, we don't have to think about it. It's just there, unless it gets challenged. Creating specific "women's bookstores" or "Black Entertainment Television", or any of a million other examples, is one way (not necessarily the best way, but there you are) of challenging these insidious structures.