My Little Pony has always been about pandering to the female demographic. In Gens 1-3 it was extremely blatant and unapologetic about it (since, in retrospect, these shows were aimed exclusively at little girls with absolutely no attempts to appeal to anyone outside of that niche). Gen 4 was constructed with far more attention to detail, whether this accounts for the more intellectually stimulating writing, as well as increased level of complexity within the realm of character progression or the extra emphasis of worldbuilding and lore in general. Incorporating a traditional fantasy world and grand diversity of creatures that inhabit it complete with various cultural/ societal variances and the like, pretty much requires the presence of more male characters since the viewers' collective suspension of disbelief would be put in jeopardy to assume the world was composed of nothing but females (as seen in G3 excluding Spike and any other minor characters I may have glossed over).
What I am trying to get at here is the dissecting the inquiry itself: "Why don't the male characters get as much focus and development?". Would there be any need to ask such a thing for Generations 1, 2, and 3? Of course not. Gen 4, however, IS deserving of this question, and even possible criticism simply due to the fact that its potential is so much higher than any other entry in the series. Most people will come to the conclusion "Oh, it's just for little girls, so deal with it". This simply is no longer the case. As far as I am concerned there remains no excuse for the male characters to be neglected to the extent that they are in FiM. And then, we must take into account the fact that nearly every main character in female, thereby facilitating much more development and focus be dedicated to them as opposed to secondary or tertiary cast members. G4's Spike being the only exception that comes to mind. The solution to this predicament? Add some goddamn male characters with overarching plot relevance who are not merely antagonistic in nature. Either that, or take an incredibly bold move and introduce some legitimate romantic interests for the Mane 7. Hell, we already have both Sunburst and Flash Sentry to fulfill that role for the two Purplesmarts; why not actually put them to use?