Because the OP is most likely gone or has found their answer, and any new posts are just adding fluff. Also, what often happens is that someone hijacks an old post to ask a somewhat related question, again, adding noise and confusion.
Re: Leave trailer tires on the floor during winter storage?
Closing thread............
12. Please do not post to threads that have been inactive for more than 3 months UN-LESS you are the original poster. We have very active forums and any thread that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old thread. This is considered a hijack. Please start a new thread of your own.