It boils down to effort/cost vs value. We disable all kinds of backup data on our android app, including local favorites (should be backed up imo) and auth data (should not be backed up). It's just a hassle to implement, handle, maintain, test and no one ever asked for it. We had it enabled at some point but then had a bug only occur when a user was restoring data from a backup, crashing the app instantly on start. Of course then it gets decided to completely disable it, instead of spending say 1000€/month to maintain/test this feature 'noone' wants.

Same as with portrait/landscape mode.