We go there every time we visit, and I have noticed that as well. Perhaps, because many people have huge houses with huge empty walls (and because they (the gallery) has to eat too), the gallery concedes. Or agrees to what the artist produces. They're really caught in the middle at times, I would think. I'm glad that I am allowed to move around there and find a viewing distance the print and I can agree on, even though size alone can't save an image I just don't care for no matter how I look at it. I've pretty much settled on full (35mm) frame on 11x14 with 3/4" borders. I've done a few shots that look beautiful as 16x20. As for the rest, I wouldn't be fooling anybody by making them "big".
I once had a conversation with an art dealer in New York who was good friends with Bonni Benrubi, the gallery owner. She sent me to go see a show that Bonni had up on the wall of platinum prints by Jed Devine. Jed's prints were anywhere from 6x17cm to 8x10 inch. Beautiful work. Bonni told her she had the show of Jed's work because it was beautiful and needed to be seen, but she was unlikely to make any sales off of it. The big "hedge fund wallpaper" color inkjet prints of deadpan ersatz snapshots, however, she could barely keep in stock. When it comes to galleries, they are as much slaves to the market as they are market-makers.