I don't even think it's that technical, though I agree Benford's law does help.
The numeric keypad is largely based off of ribbon tape desk calculators [0], which is why the + is double size, the enter (=) is double size, and the 0 is double size. The + and Enter are designed to be used by the right hand pinky, while the 0 is designed for use with the thumb. The numeric keypad is designed for five finger entry. Leaving it in that configuration means that people in an office who are used to using a ribbon calculator can more easily adapt to the PC keyboard. That's what office workers expect to find on a machine that sometimes is just a calculator.
If you go into a business or accounting office today, you'll still see people using these stupid calculators (stupid because they waste paper and ink). And if you've ever seen someone use one that's good with them, they can be extremely fast. Faster than you'd ever need to be entering a phone number (unless you need to enter the IT Crowd's emergency number).
When you use a telephone, however, you only use one finger. You're only entering 7 to 11 digits, typically.
The numeric keypad is largely based off of ribbon tape desk calculators [0], which is why the + is double size, the enter (=) is double size, and the 0 is double size. The + and Enter are designed to be used by the right hand pinky, while the 0 is designed for use with the thumb. The numeric keypad is designed for five finger entry. Leaving it in that configuration means that people in an office who are used to using a ribbon calculator can more easily adapt to the PC keyboard. That's what office workers expect to find on a machine that sometimes is just a calculator.
If you go into a business or accounting office today, you'll still see people using these stupid calculators (stupid because they waste paper and ink). And if you've ever seen someone use one that's good with them, they can be extremely fast. Faster than you'd ever need to be entering a phone number (unless you need to enter the IT Crowd's emergency number).
When you use a telephone, however, you only use one finger. You're only entering 7 to 11 digits, typically.
[0]: https://www.google.com/search?q=ribbon+tape+calculators&tbm=...