You aren't required to but you will pay substantially more by not using the app and creating an account. They offer "exclusive" deals that usually amounts to roughly ~20% off menu price, while they raised all their base prices that much or more so you are subjected to data harvesting in order to pay the normal pirces.

I order fast food all the time and I'm always scoping for deals, rewards, etc. in the apps, and it's nowhere near 20% off on average.