Unfortunately if you remove the walls from the garden you get a malware, crapware, and (ironically given the topic) spyware explosion -- a tragedy of the commons more or less. Mobile devices are used by over a billion people, most of whom don't know much about computers. From the perspective of sleazy marketers and black hat hackers that's a lot of fresh meat. They're better than PCs since they're studded with sensors, allowing the user to be tracked and spied upon to an unprecedented degree.

Look at the Google Play store and the Android ecosystem, which is comparatively more open. If you don't know what you're doing and install apps from the app store without examining them closely, you'll get random ads, trackers uploading your geo-location constantly to god-knows-where, etc.