Experiences vary. A lot of it has to do with the conditions of your local routes. I personally have never had a flat while commuting. I've had plenty of flats while MTB racing, plenty of flats on regular MTB rides, a few flats on road bike rides, a handful on bike tours... In the past five years, I've had three flats total... across about 28,000 miles of riding. Across the last 15 years, my record is even better.