Why would so many people buy free pay-to-play games?
What's confusing about this? It's just like a demo. You get some stuff for free to try it out, and if you like it, you pay for the rest. Or you can just keep playing the free version.
There should be an easy way in settings to ban all in-ap purchases
Settings > General > Restrictions > In-App Purchases > Off.
identify the in-ap enabled games on the ap browser so you'll never accidentally get one
If you look at an application in the App Store, you'll see "Top In App Purchases" for applications that have in-app purchases.
you could still end up buying based solely on the picture
That's your own damn fault then.