Just to make it clear: There are a million use cases that don't involve scaling fast.

For example B2B businesses where you have very few but extremely high value customers for specialized use cases.

Another one is building bully hardware. Your software infrastructure does not need to grow any faster than your shop floor is building it.

Whether you want to call that a "startup" is up for debate (and mostly semanticist if you ask me) but at one point they were all a zero employee company and needed to survive their first 5 years.

In general you won't find their products on the app store.