Brake cooling ... presumably, if ignored, Bad Things could happen ... like broken wheels or fires?

Seem like there are truck fires - burnt-down-to-the-frame - several times a week on big grades like Grapevine and Donner Summit. They tend to start because trailer brakes get too hot, set the tires on fire, and it goes from there. Guess not everybody has jake brakes, or they sometimes aren't enough.

I recall that in our '57 Chevy wagon, we always had to stop about 1/2-way down Priest Grade (new, not old) for 10 minutes or so to cool brakes, while coming home from our annual family trip, even with help from low gear in the Powerglide. Without the stop, they would fade away (all drums) and we would have no brakes at all on the lower part of the grade (likely bad results...). Brakes were something that US cars of the '60s and earlier usually didn't have a good set of; the switch to disc brakes helped a lot, though even they can fade and burn if badly mistreated.

The purpose of brakes (regenerative perhaps not so much if something else can use the power generated) is to convert kinetic energy into heat; often a lot of heat. I've seen videos of aircraft and race car brakes glowing red-hot and worse.