One or two miles is certainly a walkable distance, if I have the time. Riding a bike is quicker. I'll easily hike 5-10 miles. I ride my bike to work most days, 4.5 miles. None of my co-workers ride a bike to work but they are not slouches. All of them are archaeologists and during the field season when they are in the field they routinely walk 5-10 miles per day for a session that can last up to 9 days.
I have a fairly physical job also. Still, most co-workers would never consider riding/walking to work even though they're not lazy or afraid of physical effort. Personally, I think 4or 5 miles is about ideal for a bike commute. Under two miles and I prefer walking. Currently I have a 7 minute commute walking or like 3 minutes on the bike. I always hated long commutes, even when I drove to work.
Of course, there are many reasons for this. However, sadly, most people don't do enough walking to even fathom what a walkable/bikeable distance is.
Have you observed this?
I have actually observed this and all I can say is, is that people are lazy. People "NEED" to park in front of their destination, rather than park further away and walk. Personally, I was part of a two person crew doing a lane closure. About 200m down the road is a gas station. If he (my supervisor) needed a break, he drove, whereas I walked when I needed a break. From a cycling perspective (unless you are in the Netherlands or Belgium) it's really a non issue since we can pretty much pedal right up to our destination.
Why should I ask them and what difference does it make if they do sports?
Why not? Don't your work conversations centre around sports? They do here! Just about everyone participates in some sport or another ... and of course, as a part of keeping in shape for whatever the sport is, a lot of people cycle or walk to and from work. Or if they live some distance out, they park their cars several km away, or get off the bus early, and walk.
You mentioned that your coworkers aren't lazy nor are they afraid of physical effort ... so I presumed that they all participated in a sport. And it is just natural to talk about sports.