This is unusually, and I agree with you: I hope it never catches on.
That said, my previous workplace has offered entrance with cellphone, as well as entrance by regular key fob. Over time, I have seen people switch more and more to cellphone method, and either returning the keyfobs or leaving them at home.
Also, a nitpick: you don't necessarily have to purchase a cell plan for your phone. For example the scheme discussed in the article will work over WiFi just fine. And if you are in front of your computer trying to login, the chances are, you have WiFi as well. So while old cellphone is less convenient that keyfob (needs charging, bigger, heavier), it is still pretty usable.
I think many people enjoy the option of using their phone, but don't like that they HAVE to use it. For example for most occasions you have your phone on you, but for example when it is broken or empty not having an alternative would be really annoying.
That said, my previous workplace has offered entrance with cellphone, as well as entrance by regular key fob. Over time, I have seen people switch more and more to cellphone method, and either returning the keyfobs or leaving them at home.
Also, a nitpick: you don't necessarily have to purchase a cell plan for your phone. For example the scheme discussed in the article will work over WiFi just fine. And if you are in front of your computer trying to login, the chances are, you have WiFi as well. So while old cellphone is less convenient that keyfob (needs charging, bigger, heavier), it is still pretty usable.