Um... yes. I missed a flight due to major flooding on the route to the airport requiring me to take the loooooooooog way around. The flooding didn't effect the airport itself (or my flight) because I don't live in a town with an airport.

It's also very, very easy to miss a connector flight if the plane coming in is delayed, or even if the airline decides to route you through an entirely different city. I've missed a couple that way. You can get held up at customs or security when landing in a new country and that country requires everyone to go through customs and security again.

Then there is illness, accidents, and emergencies that come up all the time.