The ads in Google also started like this. (However, to my knowledge, there is no way I can pay Google to get the ads in my search removed)
So paying for a service alone doesn't ensure that you are not going to see Ads.
Once they have exhausted their potential market of paying users, almost every service will eventually resort to Ads.
Down-right joke really. The people who idolise them are incredibly delusional.
Although considering Brin's interactions with female employees etc, no surprise really. They were full of it from the off. Page is better at hiding it.