I've a friend who worked for a hospital corporation which would not allow employees to fraternize with equipment purveyors, for obvious reasons.
Heh, they've been married thirty or so years now, and, for cause not related to that question, both moved to other, better, jobs.
I see the point on both sides.
Having been around where sales pitches were routine at "lunch time" - meaning they brought us what they ascribed as a feast and we didn't get our own break time to go out, run, shop, eat our choice of meal... that got annoying, but we never felt beholden.
It is a little infantilizing, that one is assumed to lose judgement with a cup of coffee or lunch, or ... gasp, some fooling around; people are more compllcated than that, or some are. On the other hand, corruption makes the world go round, and/or the appearance of it makes the earth swivel. I can see it's important for a firm to toe the "gift line". Am a bit recalcitrant on the romance thing - which I know is a rule, at least within layers of hierarchy - at many workplaces. (I just don't personally care what people do unless it affects job performance, I always look at (er) performance. I too was stunned by the level of spy expertise thrown at this at Walmart business.
On that with a side look at WalMart's general practices, I see GreenWitch's problemo.