So yeah, I'd say the collectively conditioned desire to fit in at work is a contributing factor -- although I'm sure not the only factor -- that prevents people from feeling comfortable turning their workstation into a makeshift gym. Which is a damn shame.
Build up your (mental) calluses
If the main reason you haven't tried to exercise at work is because you're self-conscious about what other people will say or think, newsflash: it doesn't matter, provided you're not in danger of losing your job, of course. In other words, you probably shouldn't start doing lunges if you're in the middle of open-heart surgery.
Making choices that affect your health based on other people's opinions is no way to live. You need to develop thicker skin and embrace the role of "quirky co-worker." Trust me, it will be OK.
But if developing a "devil may care" attitude is outside your comfort zone, try the strategy shared by one of my other "study participants" from Facebook:
Convert the crowd
Angela VanBrackle, who runs a field office for the National Multiple Sclerosis Society, is actually the only employee at her location, but every month she and her co-workers participate in a workout challenge: "We set up various challenges: planks, sit-ups, and so forth, and schedule them on our calendars. This month is a sit-up challenge. When we have large, in-person meetings, we'll do the challenge together."