The answer for 'why do we still laugh at this idiot' is multifold.
The first is, comfort. He's simple, easy to laugh at. He's Garfield of pathetic people that are funny to laugh at. This combined with how he has this uncanny ability to infuriate people very easily using a combination of being sarcastic, sassy, bitchy, whiny, unable to take the slightest criticism or even compliments he doesn't like (i.e. the leggy incident where he got a meme out of drawing a Ladybug animation error but didn't cash in on that because he's too stupid to). He is reliable. Whenever you want to see something mildly entertaining, you can check on him and he'll still be there, in his parents' basement, living off them, gaining pounds, losing skill, losing fame and getting his dumb ass into controversies. He's a more reliable Moviebob because Bob will probably die during the 2020 election, the heart attack upon seeing Trump win killing him with the sheer rage he will feel at the troglodytes who stole HIS future HE earned.
The second is, he is a cautionary tale. For artists, specifically. He teaches people not to give up, not to stagnate, keep working, keep improving, settle for not the dream job just to get a foot in.
Dobson gave up on his dream when he didn't get a dream job at Disney, and he wanted to get in there during the times when their 2d division fucking died following the engineered failure of Treasure Planet.
He's lazy, he's a bad artist, he doesn't practice, he doesn't improve, he doesn't even follow the very simple recommendations or guidelines for some things just because he doesn't wanna.
By keeping the story of the Dob alive, we can discourage young artists from falling into his steps. Steps like 'why not just trace this fucking building, who'll care? So what if it's an original art piece I was paid for?' and 'sure, I am off-model, but it's MY ART'. Steps like refusing criticism.
I could go on but just these are enough, I feel.