True dat.
Did some pre-emptive maintenance on my Sunbeam a while back. Put in a new cap, rotor, points, etc. 15 miles down the road, on the way to a car show with the kid, engine dies just like someone turned off the key. Knew before we stopped rolling is was the low voltage side of the ignition. 30 seconds later, I was holding the broken rotor in my hand. 30 minutes later, I was installing the old one (delivered by my lovely wife) that I had put back in the parts cabinet. Because as you know, you never throw away Sunbeam parts... (Except I did pitch the new, broken rotor.)
And as a data point, I'm currently running without a spare on the Suburban, even though it has space for a full-size one. Plus, I actually have it in the garage.
Not carried due to some ongoing maintenance in the area it's stored, plus the fact that the cable hoist assembly was rusted solid when I last lowered the tire, and it took 1.5 hours and a garage full of tools to free it without just cutting the cable. No way that was happening on the side of the road. (I see they now make new, better hoist assemblies.)