To put in plainly, I HATE it. I HATE it so god damn much!
Their popularity leaves me completely slack-jawed and with faith in humanity draining very rapidly. It's obvious that they all are created in a program called "poser 3d", or was it "daz 3d"? No difference really, these programs are letting you create human characters from a basic human template model a-la videogame RPG character editor screens. They all are characterized by the abysmally bad render quality (It would already be considered bad as far as late 90s, think about that), ultra creepy "realistic" human models with limited control for facial expressions, and lots of reusage of stock assets that were either free for downloading, bought in the app's store, or maybe even just straight out torrented. So basically you have ready premade characters, ready premade assets and environments, all that's left to do os to cobble them up to a scene, pose the models into something approximately resembling a natural pose a human could take, and hit render. All that was left to do is add speech bubbles and your comic frame is ready! With that it is probably possible to chug out pages on a hourly basis.
Oh, and all of these 3d comics have rating "R". Why? Because the people that the program lets you to create are naked by default, and fully detailed. Maybe then you'd need to spend some effort to create clothes and outfit your characters with them? Oh, but do not bother, the asset resources are also chock full of pre-made clothes. Many thousands of poser "3d artists" on DeviantArt do not even bother with outfitting their characters with any of the clothes, 90% of their art and stories are about fanatical nudists.
So you see how appaling it all looks to me? It requires zero creative effort. It's far worse than those sprite webcomics that were popular at one point, because at least those sprite comics were pleasing to look at and had some aesthetic and internal artistic consistency, and many at least featured custom-drawn original sprites, or edited the sprites they had.
These things on the other hand are frankensteined out of assets made by a bunch of different people, all with a different quality level, all for entirely different purposes and styles. So they will and do clash with each other stylistically when brought in together. Add in a bare bones outdated render engine that somehow manages to look worse than even direct screen grabs from the editor window...
I would guess that what's explain the popularity is the "R" rating - since models are naked and anatomically detailed by default - it's trivial to create sex scenes with them. But who for the love of god would find scary and badly rendered, badly posed 3d model porn arousing?! I've had higher standards even when I was fricking 14 and ready to hump anything remotely female-shaped!
The only and last real explanation I have is the rating fraud and botfarms that constantly vote these to the top. But it's awful lot of effort and surely the website would have some measures against vote cheating?