I've cycled through winters with wind chill in the -15F range and up to a half foot of snow on the ground. So, it is more than doable to do in both those cities.
Everyone is not you. Can it be done? Sure. SHOULD it be done by a cross-section of the populous?
I don't see why it couldn't be done by almost anyone given that they live close enough to work. Anything less than 10 miles is doable assuming you have a good route.
>almost anyone
I think that you considerably overestimate the capabilities of “almost anyone”
Will power is a capability most people are lacking in, so I guess you are right. Most people have the physical ability, though few realize it.
Maybe proper bike infrastructure could increase the number of bicycle-commuters from ten percent to thirty percent. Think of all the space you could have for your car if there were twenty percent fewer cars in front of you.