Why do hammers put up with being smashed into nails all day?

because once you're a hammer, you're just biding your time to smash a skull.

they don't. like every thing they wear away in some proportion to their use and replicate in some proportion to their usefulness to other things.

AIs are (going to be) agents, not tools.

And what's the difference?

Agents act on their own. If the hammer looked at what you wanted nailed and said, "Sorry, Dave, I can't do that."

There are degrees of autonomy, of course, and not all noncompliance is bad. Same as with humans; biological agents.

So, the difference is that you need to delete a few bad training runs?

But it seems much easier to realign an agent until it complies. Or ditch it and grab a new one.