Came here to say this. I guess that if devs want their games to be listed as free they'd need to have two versions of the app, a free ad-supported version and a paid ad-free version, instead of using IAP.
I have actually seen devs do this, but I can't remember any exact cases.
I feel like its pretty common to see both. I see the advantage in using the IAP though since you get to aggregate your ratings and reviews in one place.
I have actually seen devs do this, but I can't remember any exact cases.