How or why has YouTube allowed me to block advertisements for over a year?

I run uBlock Origin, I love uBlock Origin.

I'm just left scratching my head as to how or why Youtube hasn't been able to force advertisements on me somehow?

It can't be that difficult for them, can it?

Just send advertisements through youtube.com instead of googlesyndication.net or whatever runs their video ads now.

How could adblockers ever block youtube.com?

I'm just curious if anyone has any insight into how I have successfully been able to block for so long. And if there is a strategy behind my being allowed to do so?