Your error is that as seen by the sky high and increasing obesity rates, for example, most people are not as motivated (due to personality or just environment), and I'm quite sure work from home will cause obesity to spike in 5-10 years (there's a bit of lag to get the numbers).
At least the commute was forcing a lot of these people to move around.
And before you start with gyms and such, remember that New Year's resolutions prompt a huge amount of people to register at gyms but a crazy number, something like 80-90% drop out by March.
But then you're in an office and you have to move around. Maybe go out to lunch at a cafeteria.
I wore a pedometer for a while. While I was working from the office I was averaging about 8000 steps, while during a full day at home sometimes the average was as low as 800 steps.
At least the commute was forcing a lot of these people to move around.
And before you start with gyms and such, remember that New Year's resolutions prompt a huge amount of people to register at gyms but a crazy number, something like 80-90% drop out by March.