Years ago my professional society was hosting a cocktail reception at some tropical resort- I forget which. A couple came up to one of our members and asked if the colored stripes on our name tags had any significance. (They distinguished Fellows, Associates, Accompanying Persons, and invited Guests.)
They weren't members, of course- they were just staying in that hotel and said they were checking out whatever receptions they could barge into. They said ours was one of the better ones!
Now we have our association staff at the door to each reception, checking for name tags.
As for Executive Lounges, most that I've used (Hilton) ask for a room number and the one in Toronto asked you to sign a "guest book" and posted a tactful sign announcing what they charged for guests. One woman came in and signed in- when they asked the man accompanying her (looked to be her husband) if he was a guest, he cheerfully replied, "I'm her adult supervision". They let him in.