You misquote me. I said "or ruin a tire." The interesting thing is that some bikes, notably tandems, have been set up to run either 650B or 700c, depending on the ride. Discs, of course. A 650B running the tires normally hyped for that wheel type is not that different in diameter from a 700c running the smaller tires normally associated with that wheel type. See: Wheel diameter with different tires ? Bike Tinker

Perhaps you meant 650A wheels, which are often used for smaller riders. However the same caveat applies for any non-standard wheel type, 26" and 700C being the standards on this continent. It depends on how much one rides and how far from home. I've ruined many a tire on crummy roads far from home. It's really easy to do. I always carry a spare, though I've lent it more times than used it. Many riders only carry one tube and a CO2 kit. I've lent those folks tubes, too. But I can only lend tubes and tires to those with the same wheel type. "call it a day" is not usually a fun option. Then there's the problem of trying to get home from a mountain road in the rain when you may not have seen a car in the last hour and there's no cell coverage. Even in less trying circumstances it's a serious PITA which could have been easily avoided. Non-standard wheels = carry spares. I ride with a guy who once had 8 flats on a single pass climb, all from different causes. He's always well prepared and finished the ride just fine.

BTW, when I flat I just throw on the new tire with a new tube. No need to look for the cause, much faster.