As a board member, I'm hesitant to share my personal opinion. I don't make decisions on the board based on personal opinion, but try to represent the best interests of membership as a whole.
The auctions, in addition being a great place for people to both sell and buy fish, are the primary fundraisers for the club. It allows the club to afford to bring in speakers from across the country who are recognized in the hobby. It allows for the summer picnic and winter christmas get togethers. It enables us to help support worthy causes such as making equipment donations to help support the resurrection efforts going on at Belle Isle Aquarium.
People coming to purchase other items based on presales have that money already set aside. They know to bring more than that in order to participate in the auction, raffles, etc. For all the people who come unaware of a vendor presence, they might just spend the majority on the vendor and have nothing left to help benefit the club.
On the topic of non-fish being offered at a vendor table, those would compete with our raffle items. We also recently started allowing a limited number of dry goods in the auction, which may also be considered in competition.
As mentioned, a swap would likely provide a better venue for vendors to hold tables.
As mentioned, I don't see a problem with presages and think those are just fine. I believe they certainly help bring more people to events who might not otherwise commit to attending.