They cause a lot of necroposting

No, that’s what am iTopic is - you’re allowed to necropost on them. They’re supposed to float around different pages based on how much conversation is happening.

Also, they don’t cause necroposting since necroposting on iTopics isn’t a thing - it’s called spamming if it’s irrelevant.

As I recall, ITopics were created to help deal with the problem of too many sticky (or pinned) topics. They were intended to be informative topics that were linked from a sticky topic. So it may depend on the specific function of the ITopic whether it should remain open or closed. As such, closing all ITopics is rejected.