If you're dedicated, commute does not reduce exercise time: commute is exercise time.

In my 20 working years, I never commuted other than self-powered: walking or cycling, depending on the distance. I understand not everyone has the luxury of this option, but the vast majority of people do, and yet decide to worsen the already bad traffic instead of a little exercise...

Great that you can do this and it is a great thing to do, but saying that a vast majority has this option (at least in the US) and just choose not to is blatantly false. Distance is just one of the parameters, but so is the infrastructure, weather, being able to shower at work so you don't start a morning meeting all sweaty, time needed to get the kids ready for school, etc. etc. It just isn't viable for many people, even when at surface level it seems like it should be.

It can be, but isn’t the most realistic starting point for someone out of shape to go from being overweight and driving already for 45 minutes (without traffic) to cycling 40-50 miles each way.. also people have kids to drop off/pick up, errands to run, etc. don’t think in the US its reasonable to say “the vast majority do”. Most American cities are not known for their bike friendliness..

The reverse can also be true, I've done 2x10km commutes for much of my adult working life and even if you wanted to push it to the point of sweating and having to take a shower, traffic usually foils the plan so you're confined to a more or less leisurely pace (ofc this can be 13 km/h or 22 km/h) and yet... I don't think it helped me a lot. It's just not a lot of "exercise", even if it's 10x30min per week.

Well, I know nothing, but to me it looks like a lot of exercise. Many people are getting less in total than what you're doing just in your commute...