Earlier quoted context omitted.
Does the PoW make money via crypto mining? Or is it just to waste the caller's CPU cycles? If you could monetize the PoW then you could re-challenge at an interval tuned so that the caller pays for their usage.
It's to waste CPU cycles. I don't want to touch cryptocurrency with a 20 foot pole. I realize I'm leaving money on the table by doing this, but I don't want to alienate the kinds of communities I want to protect.
This is an aspect that a lot of PoW haters miss. While PoW is a waste, there are long term economic incentives to minimize it to either being a side-effect of something actually useful, or using energy that would go to waste anyway, making it's overall effect gravitate toward neutral.
Unfortunately such a second order effects are hard to explain to most people.