Theymos doesn't want to disable the signatures because the traffic to the forum will start to dry up when everyone has realized they can't earn Bitcoin any more by posting. Less traffic will lead to less paid advertisements and less profit for the staff. How many will continue to post after there is no more cash? Less than 50% I would guess.
Oh, I'd say that's a conservative estimate. What with all the alts running around, if signatures were disabled this forum would be as dead as the Dash forum I just joined. It's like screaming in an echo chamber. The whole sig campaign thing is a very clever idea and I've said before that I haven't seen this sort of thing on other forums. It's very cool that people who are probably eating toothpaste sandwiches in a desert somewhere can earn a little bitcoin just by posting--admittedly, the more toothpaste the greater the language barrier, but still. And the pay rate is the same wherever the user is. I find that fascinating.
But yeah, there's that shitposting issue that just doesn't seem to ever get any better...