We can enable more close reasons, but we are trying to hold off on doing that unless there's a demonstrated need because long lists have historically proven to be, at best, confusing.
At the same time, we certainly recognize that some sites have different needs. For example, Stack Overflow already has 5 off-topic reasons instead of 3.
What other close reasons would you enable if you had more than three slots available? Are they applicable frequently enough that just leaving a custom comment when closing just isn't practical?
Update: I activated one more close reason slot and filled it with "this problem cannot be reproduced" close reason.
I may be misunderstanding its purpose, I would advise against reactivating the "this question has been abandoned" close reason. We regularly clean out really abandoned questions anyway, and you can't always predict when a question might pick up a response. Closing questions just because the asker might not be around is an unusual practice, or at least something that hopefully is not so frequently necessary that you'd need to spend a close reason slot on it.