It should be fairly trivial to deploy a number of existing FOSS photo hosting solutions to a server in your house though. Syncthing should make for trivial replication between the local instance and one at a relative's house. It recently gained support for E2EE (ie untrusted servers) so you could even throw it up on a cheap VPS as an extra backup and to allow for more reliable distribution between nodes. There's no bandwidth aggregation to be had here with current tooling though.
Or how about accessing your personal library of data while outside of the house (like while visiting family)?
Backups and professional media work from home? Those need upload too.
Consumers need symmetrical data connections, or at least something much closer to symmetrical, than any ISP (in my area at least) has been willing to provide.
People in my parents’ generation all have stories of some grandma’s house fire eating the family hoard of photos, including the only copies of Great Grandpa Frank as a child. We don’t want Uncle Steve losing those pictures just because his house is in the 100 year flood plain.