changing the tapes becomes the whole of the backup maintenance: no one actually verifies that the backup job is running properly. I've been on calls to clients who've diligently changes their tapes nightly, but the backup software has been crashed for months..
I've seen the same thing, but I think the entire backup process is something of a kabuki dance because just seeing "Job success" is a false sense of security in and of itself.
Do you know if the media is usable to restore from? Do you know if the data backed up is capable of actually being used to restore to function whatever system was backed up?
I think most places fall down on these two items. Where I work we are told to do restores from backup media to validate usability -- but just very partial restores, a handful of random files, which really only validates simple to verify data (a common file, small executable, etc). I've seen plenty of instances where the tapes (even LTO) stumbles further into the media -- is it the drive? The specific bit of media?
But almost nobody does a real restore, where they attempt to restore an entire system from backup (which almost always means multiple servers).