Sometimes you never want to hear from someone again because they have an entire history of trolling/insulting folks. Other times they are going on and on about a particular issue that has a limited duration. You know they will settle once X is done so you Ignore them for that duration. Also, sometimes you know you are having a bad day and just want to ignore them for a bit but give them a chance again when you are feeling more charitable without having to go edit your list.
I am ok with options. People can use, or not use them, as they see fit.
I am just glad we now have Ignore in the new forum software. I have only put ONE person on the Blizz forums on Ignore - ever. It was years ago and that person still posts on another Blizz game and is STILL on Ignore for valid reasons. I mostly handle CS/Tech type stuff so try to disregard personal opinions about folks I help. One person managed to get past that.