even when this is not the case, sqlite works well enough to replace maybe 80% of heavier database setup out there.
Scaling and ability to scale is very valuable, but I would guess massive premature scaling is much more common than scaling cliffs - especially as they don't get reported or have nearly as much visibility.
the fact that SQLite is a library (embedded DB) means only one node can access the DB at a time. This would not be appropriate for many apps that require HA.
There's rqlite (https://github.com/rqlite/rqlite), which looks cool on the surface but... it's a layer on top of sqlite, at which point you should probably think long and hard whether it's still the right tool or you should switch to e.g. postgres.