They don't. Look, Canada I think was the best until you proposed these laws. The short answer is that it doesn't make any sense to lock people up for no reason. If you're doing it because you think it's going to deter people, it's not going to deter a single asylum seeker. I put it to you that the real reason you're doing this has nothing to do with deterring irregular arrivals; it has everything to do with telling the Canadian public that you're doing something about irregular arrivals. It seems that electoral gains might be outweighing the financial costs.
What I'm trying to put to you is that it's a false assumption. I know that countries are looking at each other's laws and that political parties are sharing their experiences. My complaint is that claims made by the politicians and even by the administrators about the effect of legislation...and there is really no evidential base for the claims that are accepted quite blandly by politicians around the world.