If you're the type of person to smoke weed all day, I'm not sure that being at work would stop it. It's simple enough to sneak an edible or hit a vape somewhere outdoors and private. Who is to say it's not an ecig, especially if you're not doing it in anyone's face?

I think peer pressure, visibility, and lack of non-work distractions are probably the bigger thing, though. Not just in terms of playing video games instead of working but you don't have the option to get up and do the dishes, or take breaks as frequently to read, or any number of other things that are less "slacker" and more "ADD brain".