The martial arts does work well, but lets face it... people want to be able to add something to their game. It doesn't matter if you RP and want your Vulcans with lirpa and your Klingons with batleths, or if you just want some variety.
Of course, DS9 had different versions of the bathleth based on rank which boasted improved stats (this was based on open beta... so I can't testify to if they still do). But this would lend to the arguement that melee weapons are better than martial arts (unless there is some sort of internal mechanic that self-advances).
I want a Louisville Slugger. Seriously, who wouldn't find it fun to beat the stuffing out of some peeps with a baseball bat? Especially if it had this nice, wooden CRACK every time you whacked them with it, lol.