Consider this;
Your tire is ruined and you are in BFE.
Good Sam finds a service provider for you.
The service provider has to drive 50 miles to a tire shop that doesn't have the tire you want but has one that will fit.
The service provider charges you $500 for the tire, delivery, and changing since Good Sam only pays for the service call.
Now you are back on the road after a six hour delay on the side of the road in BFE.
Now you drive to a tire store and have the $400 tire removed and purchase the tire you really want for $250.
Now $750 and ten hours later, should you have carried the spare? Only you can decide.