They do, and it's also true that I have personally used all sorts of joint locks effectively. Now, I've never trained in Aikido, so you can feel free to claim that they're not the same locks. But I have played with Aikidoka, Hapikdoan, etc, and the locks I use are functionally identical (or at least, I can personally detect no difference) to theirs. And yes, I've used them against people of all sizes, who were certainly doing their best to resist.
Perhaps you should consider the possibility that the problem isn't the lock, but you.