The amount of oil required from one's hands would have to be the sweatest man alive x 5 to prevent a good connection. Corrosion on the coin cells caused by one's oil on their hands would be extremely rare. The clips that the CR2032's sit in generally have a good covered of the sides (sides and top are positive) and a large surface bottom (negative). So even if some corrosion would develop, it is unlikely to spread to all contact areas of the batteries.
Now if the batteries is exposed to a splash of water or high moisture, it's possible that water molecules could connect the (+) and (-) of the battery (since their are pretty close together) and begin to short the battery out.
The shorting of the battery could cause a leaking of the battery which could corrode with the metal of the battery and the clip.
If you do find a motherboard with a coin cell that had corroded, it's more than likely caused by water/moisture damage or a faulty safety vent on the coin cell that either ruptured or did not allow the battery to vent (which is extremely rare).
In all the applications I've seen lithium coin cells used (memory batch up, watches, led lights, key fabs, and 1000's of other applications), the few corroded ones out of thousands I encountered were caused by water damage.
Now if we were talking about a silver oxide or alkaline watch battery (such as a SR626SW/377 or smaller) with a far smaller surface area, the chance of a film developing preventing a good contact on the a similar smaller surface contact area is much greater. Developing a film on these smaller batteries in watches that have stopped ticking (yet batteries yield a voltage about 1.4V) is generally caused by either a bad watch movement or a film that has developed on the watch battery (simple rubbing off on a cloth fixes this).
