What you say does make sense, but this is one of those whether the chicken or the egg came first type situation. On the one hand, a lot of these hard labor jobs don't pay nearly enough for the average American to make a living like you said, probably resulting from the cheaper option from illegal immigrants for companies. On the other hand, education as a whole is moving with the advancing technology nowadays. Given a kid a choice, would he want to be doing hard labor some years in the future, or have some technical job working at a place like Apple or MS contributing to the fast advances of tech? Then there's the issue of having a fallback. The pay is either too low, or they don't have the know how since none of that stuff is taught in the average schools. Now at this point in the game, do you think most corporations would rather lean on the cheap labor so they can collect higher profits for themselves? Or choose to help out the average American and increase the pay to attract better qualify individuals for these jobs. With large companies being selfish and only looking for profits and self-interest, the answer isn't that hard to figure.
The real interesting thing is, with the education going on that is shortfalling the hard labor/infrastructure/backbone of a nation, the US is not the only one that is having problems. I visited Australia a few years back, and they are in the same boat, if not even worse off, because they don't have the illegals coming over to fall back on. Right now, key industries and companies are hiring at top dollar, anyone who is experienced in infrastructure work (electricians, plumbers, earth mover operators, construction workers) and most of it's due to the fact that their schooling long ago phased out those fields, in favor of the more technical studdies like computer science, doctorates or law. Now, they are experiencing a short fall of skilled hard laborers. The biggest thing they are screaming for are machinists and big rig operators. If you have 2 years of experience operating a crane, Sydney will start you at 80 grand a year. If you are excellent with the crane, then you will easily get 115 grand.
Now, you bring up the issue about todays kids choosing the computer programs over the hard labors. I don't know how true that is. It's possible that the reason the kids choose the computer programming classes and other technical career paths over hard labor, might because that is all that is available to the American kids. Case in point, we have a software engineer who is from Columbia. He was always facsinated by computers, but had to come to the US to get decent schooling. We have another guy who is a machinist, who came from Haiti when his parents migrated when he was 12. He was taking a tour of the university campus my company has dealings with, and this was the first time he was even aware of the machinist industry. He was originally going to take the architecture classes, but fell in love with the machinist world instead. He completed his studies, and then my company hired him as an intern, then eventually full time. The machinists get paid good, get to work indoors in the ac, and again, it's a needed industry in this country that has been phased out by the education system as a whole, but it's obvious that is an industry that in reality, is not going anywhere any time soon. Another point as well, in that you are right, if people are being paid less, it's because the corps are greedy and don't want to pay more than they have to, and it's sad, because the company I work for, is small, but big. It generates about 10 million a year in revenue, but they have no problem in making sure all of their employees, be that they are natural born citizens like me, or immigrants from other countries (we have the Columbian, Hatian, a Peruvian, Mexican, Chinese , several Viatnamese and a Cuban) are all paid very good wages. But, I guess my company is the exception and not the rule.