It's an interesting question. It all has to do with the nature of the wood used to make a neck.
Most necks are made from hard maple. Though the wood may be hard, maple is somewhat more hygroscopic than many other hard woods, meaning that is more readily takes up and releases water molecules from its surrounding environment. As it takes up and releases water, the cells expand and shrink respectively. That causes distortion in the wood, sometimes in the form of a warp, or a twist. Sometimes the expansion/contraction is uniform and no warp or twist is encountered. It all depends on the particular piece of wood - how it grew, how it was cut from the tree, etc.etc.
One of the best ways to inhibit the hygroscopic nature of maple is to apply a "hard shell finish" as advocated by Warmoth and others. Such finishes resist in ingress and egress of water molecules far better than an oil finish. I liken it to wrapping a piece of cheese in plastic wrap as opposed to wrapping it in waxed paper. Both will slow down the drying out of the cheese, but the plastic wrap will do a far better job.
So why do some makers insist on using oil-based finishes? Mostly because that's what many players want - it's popular. And it's much better than nothing at all. If the wood is of the best quality, cut and cured really well, an oil finish might be adequate. But I would never trust oil as a neck finish. When I want a nice satin-feel neck, I use a hard shell finish with a flattener and cut the finish down to nearly totally matt with abrasives. The down side is that the neck will gloss up again after extended use. That's when I take out the 0000 steel wool and rub it down again.
