You could replace the joltik with a R34 logo and nothing in the picture would change

The attention of the porn artists are primarily up held by Hatterene, the starters, and the human waifus and husbandos currently.
So it's to be expected that some of the potential R34 targets would slip through the cracks a bit.
There's still a good amount, it's just that the lack of attention means it's not much comparatively.