It is actually a very good question, eventhough it migh sound "funny" at first !
The answer is "low cost and simplicity" IMO.
As a pump that would work perfect for a kitesurfer (or anyone using a handpump), should be angled slightly forward in order to give a good and ergonomically comfy stance
Meaning, with todays pumps that unfortunately are flat: when you pump your kite, you always try to find a little slanted/tilted area on the ground, in order to put the pump a bit forward
In sand there is no problems of course - but as many or most dont rig up in sand, a slight forward canted pumpbase makes perfect sense