Why do they track you?
@Tony - also, the world has changed. In the good old days people read magazines and watched telly and the advertisers targeted their ads based on the types of people likely to be reading a particular paper/mag or watching a programme. Now, most people get stuff on just a few channels. Advertisers can't really target ads based on someone being a Facebook user or a YouTube watcher.
I'm not defending the advertisers - I've got a suite of shields - but I think that where they first went wrong was in becoming intrusive and annoying, just as they did by putting inserts and cardboard sniff-pages in the glossy mags, which only served to highlight their deeper behaviours. However, as this article notes, they only do it because they can and they can because the likes of Google, Facebook, etc., don't give a toss about users' privacy.