Really? I installed AdAway [1] on my Android phone and since then I have seen no ads. Zero.
The only issue is that some legitimate apps don't work, because they pull content from sits which are blacklisted (mostly stock ticker apps). I feel that's a small price to pay for not having battery and data sucking ads during my phone experience.
Yes, it requires root to install the hosts file. That's basically a one time event (I rarely update the list and still never see ads) and the battery impact is none because the ad blocking works at DNS level (as opposed to say, a system-wide proxy)
[1] https://f-droid.org/repository/browse/?fdfilter=Adaway&fdid=...