I guess if you're going to reinvent villains you may as well pick forgettable ones. One could argue they never caught on for a good reason though.
Some of them are characters who were only introduced a few years ago and just haven't had time to catch on beyond the comics themselves. Professor Pyg, for instance, first appeared five years ago and has been a major recurring character in Grant Morrison's acclaimed run on the Batman titles. He's already made a brief cameo in a Batman: The Brave and the Bold
And even if a character "never caught on for a good reason" in the past, that doesn't mean the character can't be transformed into something special. Keep in mind that Mr. Freeze was an obscure joke villain, mainly remembered from his appearances in the '60s sitcom, until Paul Dini's unforgettable reinvention of the character in B:TAS, which has been the basis for every subsequent portrayal of the character. Not to mention that Two-Face fell into obscurity in the early '50s, but then in 1971 Dennis O'Neill reintroduced the character and he went on to become one of the most important members of Batman's rogues' gallery.