1. A hard-core crowd like Buffalo's is best served by an open stadium. It maximizes the noise.
2. A lot of winning teams play in open stadiums (Pats, Packers, Niners, Steelers, Seahawks, Chiefs...). It really has no bearing on a team's success or stats.
3. Football is supposed to be played in the elements. Period.
4. Domes are obviously more expensive and I bet the increase in profits from the apparent versatility is marginal. During the winter months, it's all football. And in a place with a mild summer like Buffalo, an open stadium still works. Keep the cost down as much as possible; keep ticket prices down as much as possible; but you still have a state of the art upgrade that the league is pushing for.