Do I need a spare tire?

I prefer to carry a spare tire and a can of fix-a-flat, just in case. In fact, on long trips, I carry two spares, one full size spare and one smaller donut spare, along with a small floor jack.

I’ll donate the spare tire that Triedaq carries around his waist. He doesn’t need it.
Mrs. Triedaq

I don’t know if there are modern cars that use it, but I have had a couple of cars that used the spare tyre as part of their energy absorbing system in the event of an accident.