If anything backups are the key to high availability.
Streaming replication lets you spin up new nodes quickly with sub second dataloss in the event of anything happening to your server. It makes having a warm standby/failover trivial (if your dataset is large enough to warrant it).
If your backups are a week old snapshots, you have bigger problems to worry about than HA.
> If anything backups are the key to high availability.
Not really. Backups are complementary in disaster recovery. They play no role in high availability. Putting your data in cold storage plays no role in keeping your system up and handling traffic.
> Streaming replication lets you spin up new nodes (...)
You seem to be confused. Replication and backups are two entirely separate things. Replication is used to preserve consistency across a distributed system and improve fault tolerance, whereas backups just means you are able to recover the state of your system at each checkpoint. Either you're using a word while giving it a new personal meaning, or you're confusing concepts.
Depends how you do your backups. If you do them by replicating. They are both. See litestream [1].
With SQLite this is even more obvious as a database is just a file (or three in the case of WAL). Which means you can replicate to not just another machine (or any file system) but much more resilient object storage like S3 (most cloud provider offer S3 compatible object storage).
Streaming replication lets you spin up new nodes quickly with sub second dataloss in the event of anything happening to your server. It makes having a warm standby/failover trivial (if your dataset is large enough to warrant it).
If your backups are a week old snapshots, you have bigger problems to worry about than HA.