John Ruskin, John Berger, and Walter Benjamin instantly came to my mind. And I could go on. I think that fewer people would be able to name many music critics, but because visual art is, well, a visual medium, many people learn about it through books, and those books are often written by critics.
I think about the only "art" critic of any kind that comes to mind quickly is, um... I'm embarrassed to admit it... Roger Ebert :P
Seriously though: I'll bet money most people who know names of painters or writers don't remember the name of any critic from those fields.
In the end, I don't think it's that people don't remember the names of critics, it's that they never bother to learn them in the first place. Most people don't care, and that's perfectly fine - you have to be pretty deep into a field to care about its criticism in the first place. However, it also doesn't discredit the critics' work or criticism in general. Being famous doesn't make you right nor does it make your work more correct, after all.
In American society you could point at Edgar Allen Poe as someone who is only known for his fiction and poems, but who was a prolific critic in his day. He likely made more money as a lecturer than as a fiction writer in his later years. This has been researched a bit but sadly there are few texts that survive of those lectures, just newspaper opinions and advertisements about the lectures.
This one is one my personal favorites from the ones that weren't lost...
I'm not nitpicking, by the way, just enjoying the piece you shared.
I should add (it doesn't make me look great, but does bolster the case I'm agreeing with here) that more precisely my first two names were John Ruskin and John, oh damn it, what's his name, the "Ways of Seeing" guy -- and that I hadn't thought of a third name. (Perhaps with effort I could dredge one more out of my memory, but it wouldn't be Walter Benjamin because I confess I don't recall hearing of him.)
There just are a lot more famous artists than famous art critics. (And, as you say, the same for music.)