Use cases are generally problems with very large amount of factors that are not feasible to calculate with normal comouters, think about chemical/medicine simulation and logistics optimization or public transport timetables.

Never thought I would see Germany resurrecting its military industries, and even welcoming it with open arms

The ones I thought to see were not there, but I remember seeing a very disturbing archive on r/nsfl before that sub got locked (this was about a decade ago I think, somewhere between 2013 and 2015).