This is how you keep productivity low. Instead of spending money on equipment and training to get Canadian workers to do more per hour, hire TFWs to do less. Extract the difference in profit.
Oh and the TFW program undermines the general public's trust in the skilled immigration program since many people aren't even aware there's a difference. They see immigrants come in, keep wages low, push housing up (all else being equal), they conclude immigration bad. Anti immigration agitators don't even need to work to create propaganda, they can just point to the obvious.