The issue isn't that people are trapped at their current job (though some people may also feel that way, who knows), it's that if they stand up against poor treatment at their current job, the other companies in the field won't hire them.
Sure, another option is to not say anything at all, and just quietly quit and go to another company, but that doesn't really solve the problem; it just makes it someone else's problem.
And if the pool of companies is small enough, you also run the risk of these bad behaviors cropping up everywhere, with nowhere else to go.
If you don't like the conditions at work, adult up and try to fix it. Or find another job. Or start your own outfit. (Didn't some Google auto-drive engineers do just that?)
Writing an anonymous letter because you willingly signed a statement that you wouldn't is - well how can I put this - not something I can respect.
Walter, respectfully, I can see that you aren't interested in trying to actually understand what I'm saying, or acknowledging that things might have changed since you graduated, or respecting that someone who has worked for multiple launch providers might actually know something about them. That being the case, I'm going to end our discussion here.
Sure, another option is to not say anything at all, and just quietly quit and go to another company, but that doesn't really solve the problem; it just makes it someone else's problem.
And if the pool of companies is small enough, you also run the risk of these bad behaviors cropping up everywhere, with nowhere else to go.