You have a good point, apps will be convenient for the locals who need to buy weekly/monthly tickets.

But for a tourist hopping from city to city, it's a bit annoying. In my case I went from Basel/Weil Am Rhein where I had to have an app for the local (and excellent I may add) 3-cities ticket, then I went to Mulhouse, that's another app, then Belfort. Good thing I didn't push to Besançon or it would have been a 4-apps trip!

The developers bankruptcy forced Belfort to adopt the region's app apparently, that should have been the case from the start.