Three things:

1. The fact that Jolla (the company) does not even provide the "cloud" services that everyone else pushes their customers to use. I prefer to be in charge of my own data.
2. The familiarity of the environment. The command line, the directory structure, the development paradigm.
3. The possibility to do development directly on the device. An SDK is an absolute no-go for me for various personal reasons.

Those three things are enough for me to stick around, despite the daily frustration the damn thing bestows upon me in almost every other aspect. If at least half of these points were addressed then I would be in the seventh heaven, even without a proper select&copy in the browser and working folder support in the email client.