Most people talked about how the system was designed, but I’m going to ask about what you mean from a different point of view. What use would that system be?

Everyone carries around their own personal DNS in the form of an address book. It used to be a physical book; now it is integrated to your phone. There used to be a physical book of most people’s phone numbers, but that practice went away as spam calls became a larger problem and people stopped using the DNS book, the Yellow Pages, for looking up commercial numbers.

Second is phone numbers aren’t as valuable as IP address numbers.

The theoretical limit to phone numbers in the USA and Canada, which has a combined system, is 10 billion while not taking into account special numbers like 911 or that 555 numbers don’t work. That’s still enough for everyone within the USA and Canada to have a personal and work phone number with plenty to spare. If that becomes too much, the system can be changed to add more digita relatively easily.

In contrast, large parts of the Internet still works on IPv4. This is a problem as IPv4 only has about 4 billion IP address and every device has to have an IP address to work. I’ve got at least 5 devices that need an IP address to work while I only have one device that needs a phone number. So, the system of assigning IP addresses gets very complicated and DNS smooths that process to end users.