Generally, if you interrupt the user's flow of thought (if that's a thing) with something unrelated, they'll do the easiest thing possible to rid themselves of that annoyance, like a modal alert you threw at them, to get back on track doing whatever they intended to do. That's what all those consent popups are about. And that's why dark patterns work more often than not.

I roughly categorize UI/UX patterns into those that respect the user and those that don't. Showing a modal and making them decide something right now and right there is very disrespectful and off-putting. iOS of all things does this for system updates, low battery, and some urgent as hell alerts about your Apple ID. What you should be doing instead is use something non-blocking that can be ignored, like a notification, an icon badge, or a clickable bar at the top of the screen. Anyway, I digress.

And then, if you need a calculator, but the one that came with your phone quits unless accept the terms of use, what are you gonna do, as a non-technical person? Go to Google Play and look for a better one? Probably not.