Yeah, paying for content streaming is different than simply paying for an app that runs locally. Spotify proved that people will be willing to pay for music, as long as it is easier than piracy. Netflix’s early days (when it was actually a one stop shop for all of the available content) proved the same with TV/movie streaming. They proved that piracy largely isn’t an issue with cost, but rather convenience and accessibility.
But with a local app, that all goes right out the window. There’s no reason you’d need to pay a subscription for an app that runs everything locally and only gets sporadic updates. There isn’t any licensing to worry about, or third party systems to pay off. The only reason to have the subscription in this instance is pure greed.