Opening a zombie thread seems to be the number one first activity for most new members. They search google for a subject that they are interested in and find a thread here and chime in with their point of view. Often times the thread picks right back up again with new information on the subject. At least some of the original participants are usually still active and pick right back up where they left off, as if no time had passed at all. Generally they are opened because someone, somewhere, had something to contribute that could be informational and/or entertaining and on topic. But as soon as one appears - “omg zombie thread, zombie thread!!” Those posts are actually a waste of time to read but the original re-opener of the thread usually had something to contribute. At best all this can do is make the brand new member feel foolish and unwelcome.
To be upset about a zombie thread being re-opened is essentially being upset that the poster didn’t check the date of the thread before participating in it. But to have been inconvenienced by allowing yourself to read and participate in a thread and later realize it was a zombie means you were guilty of exactly the same thing.