Because I want to use these things when I have no connectivity. And I don't always plan ahead for no connectivity.

Given where I live, my big one is ferries. When I get on the ferry, it's a nice time to see what's going on in the world, and what the weather will be like, and maybe check work email (before I retired), but I can't do any of those in an online only world because cell coverage is very spotty. For the small handful of apps that manage a data store on the device, I can use those and catch up on things and queue outgoing messages. I'd like to make some more things for me, but native Android development is beyond my patience, and PWA doesn't have the capabilities, and some horrible blend of the two is what's wrong with today's world :p