What's Up With These People...
"what is up with these people?"
What's up is that eBay doesn't cut 'em off immediately and totally until they pony up with the merchandise or a refund. A total suspension of privileges would get people's attention, but eBay is very slow to do that.
If these sellers suddenly found that their eBay password didn't work, and they couldn't sell, buy, or look up eBay's restricted info (like completed auctions), that would make a difference in a hurry, I feel.