First: modern computers are used with a keyboard and a mouse/touchpad/trackball, and they are used predominantly by right-handed people. Right-handed people normally operate the pointing device with their right hand. The numeric keypad present on many keyboards is designed to be operated with one hand. If keyboard manufacturers put the keypad on the left instead of the right, then more people would be able to enter numbers with one hand and work the mouse with the other.
Second: all standard QWERTY keyboards have little raised bumps on the ‘f’ and ‘j’ keys. They let touch typists find the “home” position on the keyboard without looking down from the screen. On keyboards with number pads, there’s a similarly raised bump on the ‘5’, for the same reason.
On keyboards without number pads, typists have to use the numbers on the top row. Two rows of keys is simply too far to reach, so instead typists shift their hand(s) up to that row when typing lengthy numbers. If keyboard manufacturers included raised bumps on a couple of the numbers (e.g. the ‘4’ and ‘7’), then touch typists could more easily make these shifts by feel instead of needing to look down at the keyboard.
You’re welcome, keyboard industry.
Get to work.