Excerpt from a big-picture Android reality check; also see Google I/O 2016: Android's failure to innovate hands Apple free run at WWDC (AppleInsider)
"In reality the problem Instant Apps actually aims to solve is not so much a problem for users, nor even really the problem with OS level fragmentation in Android. It's the problem of Google search trying to remain relevant in the mobile world.Google I/O 2016: Android's Instant Apps seek to solve a key mobile problem
Google would like mobile users to start in Google search, then follow its search links to arrive at a result deep within a mobile app. The problem is that users may not have the app installed, resulting in a series of delays that might result in the user giving up (perhaps choosing not to download the new app, or running into an issue while downloading, or getting distracted along the way and doing something else).
The problem of the user not getting to the result Google is recommending is a bigger problem for Google than the user, because while the user is likely to eventually solve their own problem somehow (perhaps by downloading that app or a similar one later on), without capturing the user's attention long enough to complete a sale, Google can't get paid."