What is the problem with watermarks? I actually love watermarks as a solution for DRM-Free media, because they make illegal sharing more cumbersome but don't i

What is the problem with watermarks? I actually love watermarks as a solution for DRM-Free media, because they make illegal sharing more cumbersome but don't impede legitimate customers (at least in any way I can think of). In fact, I kind of feel like watermarks add value, lending an authenticity to my purchase which a pirated copy wouldn't have.