Why aren't apps letting your phone run AI locally instead of sending everything to the cloud?

Here's a thought: you're on a plane with Gemma running offline on your phone, helping you study, and it hits you—why isn't this the default? Most phones can already handle Gemma's 2B model (plenty can do 4B), open-source models keep getting cheaper and smarter, and chips are getting better at AI every month. Gemma 4B is basically as good as GPT-4o was when it dominated. The future should look like this: your phone becomes the server, processes everything locally, and you get instant answers without uploading your data anywhere. So what's stopping us from getting there now?