That's the point. The artist has to crank out one of these every day and he's obviously stopped giving a shit a long time ago so he turns in some random, uninspired nonsense to get his paycheck.
I've encountered a bunch of meme graffiti in real life. The most baffling one was that one time I had to use a public toilet, and on the left wall inside my stall there was a large drawing of Hitler as a MLP, along with a speech bubble calling for all bronies and pegasisters to unite and stand strong.
I don't even. I just don't.