When you're shackled to your desk bored out of your reinforced shed, you tend to notice these things because everything around you is immediately so much more compelling than what's happening on your computer screen.
Watching from the corner of one eye you observe the same few people shuffle aimlessly by, and then catch them again in the corner of the opposite eye as they return to their desks. Where the flip are they going, what are they doing and why does it necessitate seven trips to the same place and back within the space of five minutes?
Is it a pre-lunch/home-time time-killer? Are they trying to ward off deep vein thrombosis by being in a perpetual state of motion? Perhaps they're making the world's most elaborate, over-engineered cup of coffee by keeping all the components of said coffee in their desk drawer and repeatedly traversing the grid layout of desks, delivering one ingredient at a time. I think it's even possible that each individual grain of coffee has been allocated its own drop-off time slot window.
Some 'walkers' are more conspicuous than others as they stomp about making enough noise to wake the dead (or at least morbidly insouciant). I'm convinced one guy in particular - who I've nick-named 'Godzilla' - actually wears concrete boots because each footfall makes my teeth rattle and the entire office floor tremble in his wake.
...and weren't they technically 'walkers' before they morphed into animated corpses?