What is being discussed here is web advertising.
Remember how apps used to cost between 99p and 9.99 ... but suddenly they all went free, because not enough people were paying?
The ad supported model switched to was much more careful about retaining customers, so for example play a game, first time you die and re-spawn you watch a ad video in payment, next time you die you buy yourself back to life with in game gold or in-app purchased gold. This approach is working when publishers are careful to get the balance right.
Mobile web ads still open pop-ups, which on a mobile browser is really annoying, especially if the pop-up redirects to some app on the play store.
I don't root my phone for my own reasons, and i don't think i should need to, in order to have control of the network details the way i do on a laptop.... eg. set fixed DNS for all connections (open DNS) and allow user access to a hosts file of some kind (perhaps a non root hosts file, so it could be separated from the core system stuff google doesn't want you to mess with).