The trucking companies were desperate, but apparently not desperate enough to significantly raise wages or improve working conditions.
As a results rates can't rise very quickly, which means that trucking companies can't really afford to pay drivers any better (obviously with some and slight exceptions, and only talking about US long haul trucking).
Trucking companies could solve some of their work environment related employee retention problems for free. For example by firing toxic managers, and treating drivers with a little more respect.
So you are anti H1B ? another tangent :D