People think that the game is sexist for not having nearly as many female characters as male ones. I somewhat agree, but the solution isn't to throw in characters just because they're female, but for Nintendo to create new IPs with female protagonists.
Speaking purely from a marketing stand point, Nintendo really can't afford to have too many female protags. Their games are already cutesy. With a female lead they'll become outright girly and that will alienate the huge majority of their buyers.
The reason there aren't many female protag is obviously due to the lack of female gamers. JRPG is the only genre with a fan base (including a big female minority) that is relatively accepting when comes to female protags.
So don't expect much in terms of new IPs from Nintendo with female leads...
That said, SSB is different. Crossover Fighting games don't have an excuse to not include female reps. E.g. Marvel vs Capcom - many female reps despite having Morrigan as the only true female protag.
Sakurai should ignore relevance, in this case alone, and rep female more relying entirely on which of them fans want. Otherwise, the roster will continue to look as boring as it did in brawl (Wolf over Krytal was a terrible decision and so was Tink over Tetra). Fighting game rosters need the variety and just looks better with more female reps.
Of course it's all marketing, in the end gamers will generally sway towards whichever characters win tournaments. --- Capcom All Star dream team - Dr. Wily/Devilot/Donovan or Rouge/Talbain/Megaman(any)