They're useful to measure in that _changes_ to them are indications that something might be happening. Use them as canaries.

For example, your velocity has changed. Why has it changed? Are you bringing new people up to speed? Have you suddenly hit some unexpected complexity? Your mean time to resolve issues has gone down. Are you releasing code with simple bugs you should have caught? Have your team started picking them up sooner?

Whenever something changes there's questions you can ask, the answers to which might well help you do better. Using metrics as an early indicator of change can help.