Really depends, do they want to track people who are using ad blockers so they have numbers? Because that is a pretty important goal. Or do they want to track

Really depends, do they want to track people who are using ad blockers so they have numbers? Because that is a pretty important goal. Or do they want to track people who are using ad blockers so they can nag and bully them into disabling their ad blockers? Because that will end badly. People will eventually develop browsers which render 2 versions of the page, one showing showing ads that provides all results to javascript and css queries and one which has all ads removed for the user. If that happens, they will lose any metrics they have on who is blocking ads.