Very difficult for the agents to enforce such a policy particularly when some of the items disallowed in the lounge are hard for agents to spot like thongs.
I'm sure you mean this as a joke so I'll just say "spot the North American"
common one.
anyway I don't give a cough about what "Mr Melon" is wearing. I would almost certainly not notice if I saw him (and definitely wouldn't care). the discussion above hilights, of course, the ridiculousness of the dress code, but I've done that one to death so I won't go over my views on that again.
About shoes. It's an interesting one. I, too, see it as a safety issue. Not about broken glasses or bottles in lounges per se, but more on an aircraft. I have contrasting views with a mate of mine who totally wants to wear his thongs (flip flops for our friends across the pacific) in lounges and planes. I couldn't think of anything worse on an aircraft. Sure, when it comes to sleep on a long haul I will have shoes off, but I will have them. Quite apart from the whole "who knows how clean the carpet is" (and let's not even get into the lav situation) to disuade me from bare feet on board, just prefer a closed shoe. Would it make a difference in a crash? in all honestly probably not. Would it protect me from a runaway trolley crushing my foot? No, probably not. but other, less harmful things (anyone want a hot coffee to go astray?) or other things that can occur on an aircraft, and in airports/transport etc... I personally prefer shoes. Do I really care if others wear flimsy sandals or flip flops? no, not really. That's their choice and business (although sometimes grubby feet being covered is preferred in some situations..).
Again, for me, it's not about what people are wearing per se.. it's about hygeine, cleanliness and above all manners / consideration for others (eg: the loud facetimers and "important" phone callers). I'd care more about if "Mr Melon" was so distracted with his headphones that he wasn't aware of what/who was around him when wandering around (unlikely) than what he's wearing tbh.