Is cargo cult the correct term? I have never seen it used to mean "doing things a certain way because they have always been done that way."
Cargo cult programming is a style of computer programming that is characterized by the ritual inclusion of code or program structures that serve no real purpose. Cargo cult programming is typically symptomatic of a programmer not understanding either a bug he or she was attempting to solve or the apparent solution (compare shotgun debugging, voodoo programming).[1] The term cargo cult programmer may also apply when an unskilled or novice computer programmer (or one not experienced with the problem at hand) copies some program code from one place and pastes it into another place, with little or no understanding of how the code works, or whether it is required in its new position.
I think that applies here.
Security: Adding a layer of security on a per-filesystem basis is not sufficient or necessary. It is only conceivably useful as a backup plan when the actual security system has failed, and at that point it is not sufficient to prevent compromise.
Stability: Quotas are a superior solution.
Speed: Not an issue for /usr, which is rarely written to.
Integrity: We have journaled filesystems now. If you lose a filesystem it is almost certainly because the device has gone bad and needs to be replaced. For last-ditch system recovery, an initrd solution like Dracut works better, since it can solve problems involving the root partition.
Size: Modern computers can boot from any size partition.
fsck: Preventing fsck is no longer useful. It doesn't take an hour like it used to. If there was a power interruption I would prefer to fsck all my filesystems anyway.
How then do you differentiate between legacy cruft and cargo cult?