The kind of situation where not carrying your phone works is one where usually you either have your AirPods in your ear, or when you're driving and it is connected to your car audio, or you don't mind answering via the speaker phone.

Transparency mode is good enough on AirPods that I feel safe using them when I am cycling or running, and not having to carry a phone during those activities is a big win for me.

Of course this means getting even more locked into Apple ecosystem, but I even forget that AirPods are bluetooth devices given the way they seamless work with other apple stuff.