Getting a flat isn't what anyone wants, but at least if it happens to you, you can have a roadside service come out and put the spare tire on, right? Not always. Sometimes it's better, or even necessary, to have your car towed instead. While it might seem like an expensive or time-consuming process to have your car towed, it can protect your car in the end.
You Can't Tell if the Spare Is in Good Shape
If it's dark, it's raining, you can't really see, then you probably can't tell if the spare is in good shape. You don't want to call out a roadside assistance truck only to find your spare is unusable and the truck can't tow you. It's better to ask for a tow truck and tell them that you have no idea what condition your spare is in. Don't be embarrassed by that; the spare is one of those things that many people forget to monitor in a car. Once the tow truck arrives, the driver will see if the spare is okay. If it's out of shape, get your car towed.
You Can't Even Find the Spare
A lot of car manufacturers are trying to drop spare tires from their cars to lighten the cars up and give them better recorded mileage. However, that leaves people in a bind if they are used to cars always having a spare in the trunk because it's not something a lot of people are used to asking about when buying a new car. Obviously, if you can't find a spare in your car, you'll have to be towed.
Your Only Route Is Unsuitable
Spare tires should be used only at slower speeds, on surface streets (and not freeways), and on roads that are in generally good condition—no unpaved roads. They also shouldn't be used for too long. If the shop you want to take the car to is far away, accessible only after a freeway drive, or is in a town that is surrounded by unpaved roads (like in a rural area), you'll need to be towed.
Call a tow truck service (or a roadside assistance service who will send a tow truck to you) and talk to the staff there about the condition of the spare and your future driving situation. Services like Mickey's Towing & Recovery can help you decide whether a tow or a changed tire would be better.