... by letting the registry sell them for crazy amounts instead, and letting them continue to overcharge the owner on an ongoing basis.
This might have been true in the past, but it isn't true anymore, especially not under new gTLDs. Nobody goes around typing in <word>.<tld> domains out of curiosity anymore, and advertisers don't pay anywhere near as much as they used to for impressions on domain parking pages. The vast majority of premium domain pricing is driven by pure greed.
Which is a modern take on domain parking.