I attended the opener and I was surprised by how quiet the arena was. Aside from the occasional "let's go Buffalo" chant, my sonic recollection of the first period was the vibrant clarity of tape-to-tape passes and some guy mocking the silence every five minutes or so with his own "let's go Flyers" chant. That was one guy, but I'm sure many people who were there could hear him.
While it might not speak to Buffalo specifically, the economic demographics of sports fans attending games at arenas and stadiums nationwide are changing as average fans are priced out of the market. The nature of in-game entertainment can also contribute. The Cowboys no longer enjoy home field advantage due to ticket prices that mostly favor corporate buyers over your average fan who is probably more likely to cheer. Add to that the giant television that distracts the audience from the actual game and their new stadium is not a place that opposing teams fear.
I predict a similar phenomenon in San Francisco when the 49ers move into their new stadium. As it stands right now, season ticket holders will have to pay for the right to purchase their tickets, in the same way that rights to purchase tickets are sold at Churchill Downs for the Kentucky Derby. I believe that buy-in price will be somewhere in the neighborhood of $20,000 - $30,000. This will effectively price average fans out of the market, and the place will get much quieter.
The minimum ticket price for this year's super bowl is just north of $2,000. At those prices, what average Buffalo fan could afford to attend the game if and when the Bills make it back?
There a lot of factors of which price is just one. As for aging musicians like Gabriel, it is my experience that the energy level at a concert directly correlates with the age of the audience.