What difference does it make if the thread was created 20 years ago or 20 mins ago? If there's something that someone feels is of relevance or is useful to the discussion it makes absolutely no sense to take issue with how long it's been since the last comment was added. Those people who bizarrely get irritated and find themselves unable to refrain from making the useless "zombie thread" comments and proceed to point out the obvious but yet completely irrelevant fact that an extended period of time had passed since the thread was active are ultimately doing the site a disservice by both steering away or even derailing the focus on the topic of discussion and even worse, discouraging others from wanting to add perhaps an important piece of information to the thread for fears of being reprimanded by an ornery site member when it's entirely unnecessary.
A lot of people, myself included, use AK as an information database and often times find pieces of info shared in users comments that can't be found anywhere else so it would be a huge loss if more and more members follow suit with the zombie thread ridicule trend and deter others from wanting to join in older threads.