Most apps are built for an average user.
My best tools are built for one user. Me.
That changes the spec. The interface can be dense. The defaults can be opinionated. The data can come from weird local JSON files. The workflow can assume my morning routine, my training plan, and my current race goal.
This is why I like personal software.
You do not need a market segment. You need a real pain and a loop you repeat every week.
The rule
If I do something manually more than twice, I ask whether it should become a script.
If the script becomes useful, I give it an interface.
If the interface changes a decision, it belongs in the assistant.