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.

Yes. Mostly because of delays that cause them to miss a flight that they're connecting with.

You also have people oversleeping, getting caught in traffic, getting confused about their flight time. It happens. I've missed a few flights in my life for these reasons. (But just a few.)

Finally, business travelers do make last minute cancelations and changes on a pretty regular basis--for example, to get on an earlier flight out.

> Do people really miss their flights so often that overbooking isn't often an issue

Yes. Wendover Productions on YouTube posted an excellent video a while back explaining why airlines overbook their flights: https://www.youtube.com/watch?v=EqWksuyry5w Most of the time it's not an issue.

There can be a number of reasons for missing a flight. Two examples: a) You're going from an airport which you need 2h+ to get to, and your train is delayed. b) You're on a week long holiday going through multiple towns, you miscalculate travel time / miss a transport, and don't arrive on time.