While I certainly don't speak for 3 Rivers, please consider my experience.
As someone who owned a fly fishing shop in Michigan and also hit many of the big midwest "fly shows", I can completely understand the reasons for attending or not attending certain shows for any given year. Or even skipping certain shows for good.
First off, bow shops, fly shops and even online retailers are businesses first. If a certain event, no matter the good PR of handshakes and the like, is a big loser accounting wise, a responsible business owner must take that into account. While maybe unpopular, losing money instead of making money is a poor business model.
Also, the set up and takedown for a show, especially if you know you're going to lose money, becomes something you don't want to do, especially if you know you can make more money by not going.
Don't take this the wrong way, but many sportsmen/flyfishermen/hunters are very passionate about their sport. What they often fail to realize is, those in "the industry" of supplying the goods we love and require, if they are to be successful long term, they must also understand that the bottom line comes first. Cold, but true.
Going to shows that cost money instead of make can be done occasionally, but keep doing it and you won't be in business long.
I'm not sure what everyone here does for a living, but be it a truckdriver, plumber or a banker, doing business that loses money, no matter how much you'd really love to do it in your heart, is just bad business.
I hope everyone takes this into full consideration.
Again, I certainly can't speak for 3 Rivers, but I hope everyone keeps in mind that, even though those with booths at any show love hunting as much as you, they have the bigger concern of paying the bills within their passion.
No matter your business, you have to be smart and keep the bottom line in the black, instead of the red.
My guess is, if any business made enough money at any given show, they'd do it. If you lose money, even though you'd love to have a booth and shake hands, it just is a terrible business decision.
Unless you've owned a business that's also your hobby/passion, you may never understand what I'm trying to convey.