I think that it does not have to do with people enjoying the sports, but being able to play it either now or when they were a kid. Think about it. Football costs just that a football, base ball costs a ball,bat and glove and in some cases you just need a stick and a ball. Hockey on the other hand is much more expensive in comparison to the others. Another thing that plays a role is the fact that the arena cannot hold as many fans in comparison to other sports. That drastically cuts the revenue.
As for your reasoning for canadian teams leaving canada, they would have stayed there if the Can$ was worth more. Don't you think that if the US$ was less than the CAN$ they would move for the same reason? the fans would pay 2 times as much for the same seats. that makes things harder when the fans can't always afford the "cheap" seats.
