Pokemon games are full of Pokemon! There are hundreds of them, so why this thing specifically then? Simple. Unknowns suck... even Magikarp is better than them (if used properly. Oh, Magikarp also evolves into Gyarados!)! Their stats are terrible, they don't evolve, and they can only know one move -- Hidden Power, a move that literally any other Pokemon can easily learn.
Besides their lore in the Pokemon games, don't ever have one on your team! They won't be able to defend you, and will drop like flies if you try to tackle a gym, Pokemon League, your rival, and more adversaries.