Because we can’t post covers … seriously.
You know, I was just thinking how frustrating that restriction is. Then I thought, but the effect on me personally seems to be that I'm actually motivated to produce original material, which is what I really want to do most anyway, so I can't complain about that!
I find the "BIAB Only" restriction frustrating, too, though (almost) completely understandable. I do wish it were OK to post non-BIAB material somewhere. I actually find myself thinking of ways to add a BIAB drum track or whatever to a non-BIAB thing to get it to qualify, but then I feel like Farmer Hoggett writing "pig" on the sheepdog contest form.