> Or are the jumpers only used to give the board ""feets""?
Yes this is the reason, otherwise the pins tend to scratch the desk surface and often also bend.
The jumpers also are supposed to result in some clearance for the other pins above the desk surface.
This also serves as a convenient "store" for the jumpers, which may come handy at times.
(Unfortunately, on Nucleo-64 boards, the pins are already populated and they are the long variety (which is good for attaching them), but the "feet" jumpers are not populated at both ends and even the two which are, are not of the proper variety i.e. they are not long enough.)
JW