Americans won't walk from the corner to the store across the street to apply for a job. Some of these immigrants walk a thousand miles in hopes of having an opportunity to get a job. Americans, for the most part, have plenty opportunity and turn it down. This is why there are deficits in skilled labor positions.
Yes there is money in those jobs, lots of money. A good roofer can make 6 figures. Some of it is hard work but a lot of it is also skill based pay. If you know a good mason or painter or anything in the trades, you probably keep that person's information handy. You can go through too many ass clowns just to find one real tradesman. With so many crossing, the ass clown to tradesman ratio will get worse if there isn't a trades school for some of these people to attend.
My comments aren't altruistic. I would like to see better skillsets in the trades. I don't care where they come from.