Comment by Pfhreak

Those folks who are not interested can say, "Nah." and if their partner presses the issue that's definitely problematic. A signal of "I'm not interested" should be the end of discussion, there are plenty of tools for folks whose partners aren't in the mood.

That said, there are many folks who aren't enthusiastic about the act itself, but have enthusiasm for the outcome. Many asexual folks I know, for instance, are enthusiastic that they can do something that makes their partners happy, even while not particularly enjoying the act. You are interpreting my definition in only the narrowest possible lens.