The HTMX-oriented response would be, if you anticipate needing to know how many rides a car has completed, why not calculate that on the server or in the database, as opposed to in real-time on the client (in which case, presumably, you need to deliver a LOT more data to the client, such as a full list of all rides so you can calculate those which this one car was involved in).

> I don't see which real world use cases are tackled by htmx

Because you are prioritizing state on the client. Free yourself of that, and the use cases for HTMX start expanding enormously.