I see nothing regarding adwords and app install even though its mostly legit. Is it because adwords display is expensive? Less ROI? I am wondering because targeting is pretty good and there is traffic obviously. So why?
My first thoughts, when people look for a certain app they use the app stores instead of Google. This is an overall trend by the way. Big players "stealing" search traffic from Google. For example Amazon -> books, Trivago - > Hotels.
I used to push apps on google display network with banners, it worked pretty well. On adwords search, it wasn't so easy because of the high bids. I ended when it stopped working for me, the problem was that the broad appeals app that worked so well got saturated.
I'm pretty sure it can still work, if you can find the right apps.