A winch is a "nice-to-have". Without one, but with the right ropes, pulley blocks and levers, there's nothing you can't accomplish that a winch could do, but the winch does it a whole lot more easily.
In over two years of expedition travelling, I used my winch perhaps 20 times times. I can't think of a single occasion when it was "necessary", because one can always bypass, use a high-lift jack, get a tow, dig, cut, push, or otherwise use a little more ingenuity and sweat than a winch requires. But why would you?
But it does mean that when you are prioritising what to take with you on an expedition, a winch isn't on the list of absolute essentials.
If you're planning a multi-vehicle expedition, of course, there's certainly no need to equip all vehicles with winches.