The dudes on romance novel covers are hot. I want to see them making out with each other instead of with chicks.
In all fairness, most covers show only the “almost” kiss, where the faces are not quite touching. I point that out because there are some really nice m/m covers, but few show actual “making out.”
Unfortunately there is a shortage of f/f that isn’t male-written erotica (as opposed to romance written by women, or even generally FOR women), so the covers for those tend to go farther — but farther off the path of tasteful, too.