Like all a/c systems, these gadgets needs lots of maintenance.
The trouble is when you need lot's of maintenance it becomes a problem by itself to bite you.
Some fail-safe features have their own hidden faults and since they never get used in most of the life of an aircraft system, you don't know they are at fault or won't work when sorely needed.
I have seen too many assumptions in reliability of detection or prevention devices that were never validated during manufacture or installation.
Like a "jezzuz bolt we need balances in our attempts to minimize since we can't seem to prevent anything for sure.