Only if they make changes to governance things... otherwise, just upvoting posts will not allow votes for witnesses to count. So if they don't update the governance things, they can keep voting for posts, but their votes for witnesses will eventually not count.

I am not sure why they don't get removed, but likely to protect the chain on "useless" operations that increase the costs (VESTS) of operations.

By I understand it creates a "visual" thing if they would get removed. Indeed... MayB1Day