They know, they can, they won't IMNSHO. I'm glad because I fear each program modification!
The millions are pushed up by the eternal life of players. Many cease to play after a certain time, some are thrown out and blocked. Alas, they all continue to exist as "dormant" accounts, in CC and user lists. You won't find the blocked ones in searches but when entering their profile URLs.
Only very few demand to be deleted, and this may be granted.