Agreed. I think they started it because people would grab a paid app for a one-time need and then return it after using. I saw this happen a couple times with an app that identified plants from a picture, another that scanned and removed apps that show full-screen ads, and a couple others, so the use case makes sense.

But still I think it's a mistake because 15 mins is not enough time to know if the app is going to work. Sometimes it takes that long just to get the damn thing installed! Especially if on a mobile connection or the app is big. I once got screwed because I bought an app that didn't work on my device, but I couldn't find out within 15 minutes because my storage was too full and the Play store refused to install it until I cleared out more room. It took a while to go through all my stuff and back them up to the cloud, so by the time I actually got the app installed and found out it didn't work, it had been 20 minutes or so. Now I'm very hesitant.

IIRC a long time ago, game devs would complain to google about people abusing refund policy by buying their games, complete the whole playthrough in a day, then requesting refund. This was before in-app purchase become the norm though, so you can buy full games upfront instead of unlocking it bit by bit via in-app purchases.