It's not. I still use the remote or homelink buttons in the car, when I'm in the car. But, I've upgraded my openers so they are connected to the Internet (and thus the app on my phone) for several reasons. I can open and close the garage door from my lawn tractor. I can assure my wife that "Yes, I really did close the garage door" rather than going back to look for the millionth time to reassure her (and if nothing else, the upgrade also allowed me to set them to auto-close after a few minutes). If the UPS/FedEx guy wants to deliver a large package on a rainy day and I'm not home, I can see him and talk to him from my doorbell and open the garage for him to put it in a dry place.
It's also nice to have push notifications when the door gets opened by someone else, so I'll know if I'm getting robbed by one of these garage door hackers.
Because carrying around separate garage door opener, video doorbell communicator, fire alarm monitor, weather station, etc. would get pretty bulky.