Why can't Android manage to do basic security things, like disable the accelerometers during keyboard input?
One example could be a pedometer / activity tracker app that totals up your number of steps per day. Suppose the user decides to get on a treadmill and walk for 30 minutes but finds it boring so they text their friends while doing it. Maybe they have the keyboard open the entire time, so at the end of their 30 minutes of exercise, the pedometer registers zero activity.
Or maybe you have an app that uses certain accelerometer-based gestures to trigger certain actions. If Android gets an update that turns off the accelerometer when the keyboard is open, many users won't understand why the gesture only works sometimes, and the app developer will get a ton of bug reports.
And you'd be creating these potential problems to solve a privacy leak which doesn't seem that severe given that it can only give you weak information about a person's pin.
I'm not saying that shutting off the accelerometer isn't ultimately the right decision, but I am saying it's not a no-brainer.
As to weak info, you do it again and again, I'd say it's pretty good info.
I don't think that PIN is the only sensitive information that matters, though. Android supports a numeric keypad input mode for apps. If I'm entering my credit card number into some app (Lyft, Amazon Shopping, etc.), that seems pretty sensitive. Maybe more sensitive than the system PIN even, because if I know your system PIN, I can't necessarily do anything with it unless I have physical access to your device or you've re-used the same PIN elsewhere.