I'm not defending the practice by any stretch of the imagination (it's wrong to hotlink, simple as) but I can remember in the heady halcyon days of the early internet (back when Windows 95 had yet to become a thing) hotlinking was done out of pure ignorance about the impact it had on the hosting site and most doing it knew no better nor of the impact it had on the hot-linked servers' resources.

Given that Eternal September remains a thing to this day, I wonder if that remains the case?

As for Google Bot being well behaved - I'm glad to hear that this has changed because at the turn of the century (which is the last time I dipped my toe in to self hosting) it certainly wasn't well behaved in the slightest and it would ruthlessly crawl away, happily ignoring any robots.txt limitations applied.