WHY do calculators start at the bottom and the phone starts at the top?

The calculator is the successor of cash registers and mechanical counting machines. That's why the numbers on the calculator from zero to nine are from the bottom to the top.

Until the 1960s, dialing on the telephone was done with a dial. Then tone dialing became possible, and the familiar dial was replaced by buttons.

There were many different attempts: they were arranged in a circle, or in two rows... But as a result, the familiar option was chosen, where the numbers are arranged in three rows in ascending order (from top to bottom).