Biologists often wear rubber gloves when doing their research to protect them from the nasty chemicals they’re working with and to protect their samples from contamination. I’ve been known to bitch about people not removing those gloves prior to entering common areas — touching things they shouldn’t be touching with gloves. This could lead to mutagens, carcinogens, and simply abrasive reagents on doorknobs and elevator buttons that other people touch with their bare hands. Or it could lead to environmental particles on the gloves which could contaminate and ruin some experiment. The chances of such events are fairly low, but failure to remove gloves indicates that you are inconsiderate to the safety of other people and could care less about the fidelity of your results.
It appears the equivalents in the medical setting are lab coats and scrubs. From this Science Creative Quarterly article by Timon Buys:
But this is just so incredibly thoughtless that it just screams to be railed against. God only knows what kind of work these people do. Can you imagine if someone from a level 3 lab was pulling this stunt? I would hope that people working with that level would have more sense – and it’s likely that they do – but we can’t know for sure when we see that white coat out in public, can we? I mentioned that grease stains would make me avoid a befouled seat like the plague. In the case of the public lab coaters who take up residence in my coffee shop, I might be avoiding those seats so I won’t catch the Plague.
Just as with the gloves, the chances someone will fall ill because they sat in the same seat as a lab-coat-wearer are low (although the possibility is there). It just makes you look like an inconsiderate (or ignorant, or stupid, or fill-in-the-blank) moron.