I've looked into these kinds of policies a couple of times now, and the premia are just astronomical. (At least from the quotes I've been given).

It's kind of understandable, given that the risk is not all that low. But my guess would be that it's amplified by fraudulent claims in relation to psychological illness, burnout, etc. I asked my insurance guy to exclude those, but, apparently, it's something he can't do.

You can kind of see, how this works for a roofer: If you hurt your leg and can no longer climb a roof, the policy pays. What does it take for me to no longer be able to sit in front of a screen? Well, it would almost have to be something in the psychological realm. Sure, there's the possibility of an illness with chronic pain or cognitive impairment, but those are orders of magnitude less likely, so the psychological stuff is what completely dominates the high premia.