Years back I had the ability to memorize just about anyone's phone number. Part of the skill was pure memory tricks. Associating the person to an area code reduced the need to memorize 10 digits. Then there was repetition. The more you called someone, the easier it was to remember their number. Next was we had a dialer, then touch tone buttons, All that created touch memory.
But with the arrival of the smartphone, integrated address books on our PC's and more, we lost the need to keep the numbers in our head, as it became easier to just simply tap and call. Instead of remembering numbers, we simply assigned them to the devices or directories of our choice. That model was great in the era of one phone system to call them all, but today, people are on more than just the traditional phone number.
Today, people call each other using Skype, Facetime, WhatsApp, Facebook, WeChat, Telegram, Signal, Riot, Hangouts Meet, Duo and Google Voice. We use services like Dialpad, Telzio, 8×8, Vonage. We place calls using apps or through the web browser. And, we use all these services to talk to others the same way we have used the phone to reach someone. But given the advances in technology, we no longer use the same mode of calling. But the result is the same. A conversation is held over the phone.
That's why it's time for the contact directory to start to include labeling and hooks to the apps that we use best. For example, I almost never use my mobile operator's number to make a call to someone in my directory. I use Dialpad or GoogleVoice. Sometimes I use Skype Out. They all allow me to present numbers that are known to the people I call, especially when I'm international, on a local SIM.
So while Apple's iOS's CallKit was a major advancement, the next needed one is with or contact directories on our smartphones so the app or service we use can be called, so we can make the call without having to switch between apps.