I'm in the domain industry (created a tool called Newsy - https://www.newsy.co) and this is where the domainers take the opportunistic sales to established companies who can buy their .com domains they've been holding on for so long.

You may not like domain parking industry, but for people who have decent set of .com domain names and many of them generate thousands of dollars through just ad-clicking, it's an absolute no-brainer to continue on with this trade and they will always say "it's an investment" and "it's like real estate".