Apps are easy to replace, the web is not. Google thrives in a massively fragmented world because that's where search matters. Google dies in a single platform world owned by Apple.

Fragmentation makes developers' lives more difficult, makes users' lives more makes difficult, but drives people to the web as a unifying platform. Google's cost of customer acquisition may go up in the short term, but Google still makes all of the money from search at the end of the day.