I don't think the button itself is a good idea, but it represents a legitimate concern.
When I answer a question, I am trying to help one specific individual. I don't know who else will benefit, so that's less immediate. If I have reason to believe that the OP is going to pay attention to my answer, that's incentive. If I have reason to believe that it will only help some future searcher, that's much less incentive.
A low accept rate suggests that the OP is fond of asking questions (perhaps in an attempt at cheap rep) and not following up on the answers. That makes answering the question less attractive to me, and apparently a large number of other people.
Now, somebody writing a question really should be aware of this, because it's something the OP can do to get better answers. The question should be "How do we notify questioners?", not "How do we avoid insinuating any possible rudeness?" or "How do we get the knowledgeable to put more work into answers that are likely going to be ignored?".