Google said on e-mail to developers it has deprecated Chrome web apps, and has closed the app section of the Chrome web store, as it originally said it would do August 2016.
It seem less that 1% of users actually make use of the the apps, so it impacts a relatively small number. If you have any apps they will still work, but during early 2018 it will eventually remove support entirely. Progressive web apps (PWAs) are the way forward. Google removing Chrome Apps support for Windows, Mac, Linux
Note, this does not impact Chrome extensions.