Factors like risk, access, and proximity matter.
Actually, geography can & in many cases does feature prominently in the equation. There are people out there who would definitely think twice before considering the possibility of screwing around on their spouse with someone in the same general area that they live in - not because they don’t want to, but because the possibility of getting caught is higher. Also, many guys don’t want to deal with the possible risk(s) re: sleeping with a married woman who may get into a fight with her spouse & then show up on his doorstep with suitcases & kids in tow. In addition & even more importantly, a married woman’s husband may come after the guy, etc. Ditto for women wanting to sleep with with married men.
Conversely, a woman (or man) travelling out of town - especially to a city thousands of miles away - and having a short-term fling/affair with a local (or even a fellow traveler) is much less likely to get found out.
That all being said, I agree that screwing around with co-workers is not a good idea (whether you go out of town or not) for all of the reasons already mentioned.