Imagine yourself buying (with your hard earned Poke Coins) a set of three incubators, for hatching 10km eggs. Imagine using one of those incubators for a 10km egg waiting in your inventory. Imagine walking 10km across several days. Imagine your 10km egg hatching an effing Gligar.
I’ve hatched 5 or more Gligar from 10km eggs already!!! It doesn’t evolve (currently) into anything, it’s not strong enough to defend Gyms nor beat Gym defenders. I don’t know why Niantic put this Pokemon into 10km eggs and why it seems to be so common. Walking 10km is no joke, getting a Gligar out of all that effort is pretty disappointing.