There is a quite clear usage pattern to support this behaviour: unless I explicitly say so, I don't want apps on their own to "do stuff" no more than I want my Ubuntu to "do stuff" while I'm doing something else. I only want the application to respond when I'm viewing it.
On Ubuntu, I always disable stuff like evolution server and automatic indexing after a fresh installation. At least you can do that on Ubuntu, that isn't necessarily always possible on locked-down systems. I'm happy that Android is quite usable these days because of Doze and background task killing.