This is the reason. People can talk all they want about weather, stadium size, etc., but the Buffalo Sabres have opened up people's wallets (whether on tickets or merchandise) that might normally be spent on Bills tickets.
I believe that the so-called "casual fans", who in previous years may have used up a "sports budget" on Bills tickets, already spent it on a couple of Sabres games and a new Ryan Miller jersey.
Think about it.
The Sabres are enjoying unprecedented success, not only at the box office, but in merchandise sales as well. Five players on the Sabres have jerseys that are among the top 10 OVERALL sellers in the league. The NHL says sales on Sabres merchandise is up about 1000%.
Now, you have to figure that for these fans who are spending a hypothetical sports budget on the Sabres rather than the Bills...would they like to watch the Bills game on TV? Yeah sure, but it's not the end of the world. It's certainly not worth him or her driving down to the Ralph and plunking down another $100+ that's already been spent on the hockey team.
You tell me what the WNY sports fan is spending his money on these days. Not Bills tickets. Not hard to figure out.