I suppose, to the extent there isn't already a wide market for male dresses, it's because female fashions are considerably more ridiculous than male ones, designed to emit whatever notions of sex appeal the out-of-touch people designing those fashions hold. Females in male attire look normal, but males in female attire often look ludicrous, and that's a dead giveaway of the lingering sexism in our fashion industries. Once you can begin to discern that reliably, you'll see that the females in female fashions often look just as ludicrous.
But, yes. Dresses as a concept, or at least skirts, have a limited functional merit, and it'd be nice to see more male options available for those who want them.