I carry spare tubes, a patch kit (or 2), and a tire boot. As has been noted, folks on this site tour and need to know how to fix a flat. You’re everyday-let’s-go-for-a-bicycle ride person probably not only does know how to fix a flat or carry the tools. As an ex-bike mechanic (my post retirement job also now over) I saw plenty of people bring their bikes in to get flats fixed, and when you look at the non-flat tire it is little to no air in it - but it passed the I pushed it and it felt firm test. There are so many places selling bikes, many of them poorly put together by the produce guy, and the buyers get no education on what is needed.

To be honest I took a ride years ago, when I had my 3rd flat of the day (luckily only 4 miles from home I called my wife. 😞 But I was using a different tire than usual and dumped it when I got home.

Hi Ed

I also have the "dump the tyre after three flats in a row policy".

Mike

That's exactly what I carry in the kit for my Bike Friday.  As Scott Anderson has mentioned, 20" rims + Schwalbe Marathon tires = REALLY hard dismounting and mounting.

I've had my set since 1979 when I bought my first "good" bike; I also bought a set of tools (including those steel tire levers) to go with it.  In those days the tool set included open end wrenches because the axles were solid and had no provision for quick release skewers.