When you have a smaller population the ratio of constituents to elected member goes down, making lobbying more expensive. We have just as many MPs as the US has senators and a tenth of the population.
My guess is that lobbying is less intensive in Canada than in the US because it is very difficult to do legally. I watch a commission in Quebec about the alleged local corruption and I am stunned to see that most of what is at stake there would be absolutely legal in the US.
wikipedia says Canada has 308 MPs and 108 senators; and the US has 2 senators per state and 50 states so 100 senators. US House has 435 reps.
Still a good point re: population per representative