Yup, all streamers earn a lot more money from subscribers than ads. You can see that in their streams. They pay more attention to subs and most hardly ever run ads.
This is actually a good point, many of the higher viewer streams I see don't use ads all that much and many of the "full time streamers" really seem to value subscribers yet I imagine a strong reason for this is that a subscriber has a good chance at also being a donator. I Imagine twitch also uses subscriber numbers as a sort of measure as to who gets featured more often and such.