The number pad is another example of this. Typing numbers is massively more comfortable (and quicker too) on the number pad than it is with the row of numbers just below the F-keys.
The amount of desk space people save is so negligible, particularly when people who buy these keyboards typically work in “paperless” offices, that I never understood the appeal.
I guess it boils down to people wanting their keyboards to look pretty rather than being actually useful.