Mapping key positions by row and column requires less complex computer hardware; therefore, in the past, using software or firmware to translate the scancodes to text characters was less expensive than wiring the keyboard by text character.
However, many types of computers still use their traditional scancodes to maintain backward compatibility.
With luck, the scancode (or some part of it) will be specified in the resulting "stuck key" error message.
These were initially assigned so that ignoring the E0 prefix (which is in the key-up range and thus would have no effect on an operating system that did not understand them) would produce reasonable results.
For backward compatibility, the 3270 PC translated these to XT (set 1) scancodes using an add-on card and a BIOS extension.
On the 84-key AT keyboard these were largely a subset of set 3, with some differences caused by the revised layout (for example, the position and scancodes of the function keys changed).