This is plain wrong. You can very easily shift and people do shift. You just interview with a different company, just like a citizen would.
This is even worse if a company brings you in through some other visa like a TN-1 or L1 (NAFTA and Intracompany transfer visa respectively), and then make you convert to an H1-B before they will sponsor you.
A word of advice: Always use your own immigration attourney and not the one being paid for by your company. If the company is paying for it, the attourney represents the company, and not you.
Here's a link: http://www.tnvisabulletin.com/tn-visa-adjustment-of-status/
I've seen a couple of people do this, and it allowed them to skip the H1-B hassle. You just have to be honest and show that your intention initially is just to work and return to Canada, but your future intention is to become a permanent resident.
My preferred reform would be for H1B to be fully unrestricted. If you're going to allow labor into the country, let it compete on fully equal footing with domestic labor. For the reasons Smith articulates and you've either failed to read or are intentionally choosing to ignore, employers already have the upper hand.
A better balance of power would be to repeal anti-unionization laws such as the Orwellian (100th anniversary of his death by the way) doublespeak "right to work" (really: "right to fire, and disrupt organization attempts") and ensure that labor has the same access to collusive collective action and mobility as capital and finance.
I also saw the effects of the liberalization of immigration regulations in the 1960s which saw floods of foreign students, many Indian, Chinese, African, and others, which had profound influences on US academic institutions, the communities around them, and, to be honest, on their home countries, one of which was a brain drain.
On that last point: one of the arguments for increased global wealth and/or population is that it would increase the number of geniuses and intellectuals (along with the rest of the population, one might suppose). That's possibly true, but I strongly suspect that the existing mechanisms for recognizing and promoting talent have already encroached on much of those possible gains. Not all, but a considerable fraction. Which means that the additional benefit would be smaller than a naive estimate would suggest.
Teaching opportunities are not good; there are far too many PhDs awarded compared to job openings for university positions.
It may be a benefit for private industry work, but remember that a PhD is primarily about showing you can perform rigorous scientific research, and compared to a Masters, matters less (or not at all) in jobs where research is not the focus.
You can interview at, accept an offer from, apply for and receive a new LCA for another company all while continuing to work at your existing job. This means you have a new job and (preparatory documents for a new) visa set up before even giving notice and triggering the 10 day period. I know this from personal experience (on the E3).
More specifically: in a case where an H1B holder had concern for employer retaliation (say: working for a sketchy, illegal, or otherwise undesirable firm), and was looking for an option to leave (or possibly whistle blow), the fact that not having employment would be grounds for deportation within short order would be a constant threat.
I've known many people over the years who've had varying levels of frustrations with emigration issues. Many spent at least some of that time as undocumented, what some like to call "illegal", including working without authorization. For others it was merely the frustration of waiting while an impenetrable and slow process worked its way, with several having to make unavoidable trips out of country to be able to retain eligibility, often leaving work, friends, family, and homes for extended periods (sometimes with greater levels of support and assistance). And this isn't just a DESI situation: Europeans, Canadians, east Asians, doctors, programmers, healthcare professionals, researchers, nurses.
Most eventually settled in the US, some did not.
All had a considerable toll taken on them.
its not hard but no way is it as simple as being a citizen.