If you choose not to carry one, will you carry the old wheel? If not, and you need assistance, it could be difficult to find a wheel and tire on a weekend or after hours.
I've been in places where it could take 2-3 hours for roadside assistance to even get to me, let alone obtain a wheel and tire for me. I've also been in places where there is no cell service, so getting roadside assistance could be a significant problem.
If it were me, I'd carry a spare. I know how to change it, and I'd rather be back on the road in 20-30 minutes instead of waiting an indefinite period for roadside assistance.