MNJFLA - Why not have your own house parties? That way you have control over the couples attending. I have had cases where a couple comes to a party with the intent that only the guy is going to play 99% of the time. Unless the guy is exceptional and I'm looking for "guy heavy" parties, they would simply fall off my invite list. Problem solved.
This is a common problem in open invitation LS parties, however, if the Mrs had an exceptional time at such a party, it's still a win in our book. We are an unusual couple in that I generally play way more than the Mrs at most of the parties we attend (by her choice), so if the roles are reversed, I'm happy for her. Hell, I'll even send guys she likes her way at times.
The concept of "I'm supplying my wife for guys to use" is one way of looking at it, and one that is likely going to set you up for frustration. Who's to say that the Mrs can't use these guys for her enjoyment? Rarely is sex a one-way street.
Again, I get that the primary rant is that this doesn't seem fair, and I can agree to a certain degree. If a so-called couple is really just a guy with a girl that has no plans to participate, then they are misrepresenting themselves. Even worse is it feels like your wife playing with said guy is just enabling this situation.
Luckily for us, we have control over this at our parties and we are not attending others where this consistantly happens. If it did, my wife would be turned off to learn that a couple was misrepresenting themselves like this and would simply avoid the guy/s in the future.
The guy that is reasonably attractive and married to someone that is a lot less desirable is a differrent beast, and could be a reason they're in the LS. This situation can certainly be reversed. So long as both are willing to participate though, it just is what it is. Normally that's the beauty of parties is that you both have other options when that happens, but not if you're pouting.