Threats: mmm, Russia maybe? Turkey perhaps? Neither of whose armies could be stopped by any European nation or perhaps even coalition of the same. Neither are without form, shall we say.
Or what of the EU collapses while the rising nationalisms continue to rise? Then there's Iran, China ... There's probably more.
Hopefully none of these will come to pass, but strategic planning can't proceed based on crossed fingers.
As for snipng - get outta here D

- you're changing the question and then insisting on a simplicity that doesn't exist to try and ram raid your way to a conclusion. It's sadly reminiscent of too many of the Indy related threads where trident comes up. Searching for trident and austerity brings up hunners of threads. That's probably threads featuring one or both as I don't know how to get search to return only those with both.
But the one I quoted is the first I opened and typical of countless references to cancelling trident as a contributor to avoiding cuts. If you're telling me you've missed all these other than your own mentions and / or that you, and in your opinion, others, have only a negligible contributor in mind... Well, I find that surprising.
Finally, now I have reminded myself of some more of he detail, I think the additional 70-100m a year (which is actually what the trident bit would be closer too) in the Scottish budget would be nice, if a rounding error in NHS terms alone.
Whether it's worth its in terms of what trident brings as part of a deterrence capability is where my knowledge runs out. Your point about wars that have happened proves only that mans appetite for it is inexhaustible - precisely why avoidance of cataclysmic wars between major powers has been such a notable achievement of nukes.