Why must I Sign in to iTunes Store so frequently?
My iPhone running iOS 9.3.1 and before that 9.3 frequently and apparently randomly requests that I "Sign in to iTunes Store".
This alert window appears within various apps and occasionally I get a notification on the lock screen.
How am I to know that all of these alerts are legitimate? That is, what if one of the apps just pops up this request every so often in order to grab my AppleID credentials?
Even if they are all legitimate, why? This appears when I am not buying more apps or music, I'm just using the apps I've already purchased, or the phone is just sitting there doing nothing -- why must it re-authenticate with iTunes Store?
This seems like a horrible model to train people to type an important password in response to spurious random requests.
iPhone 6s Plus, iOS 9.3.1