Those activities only fit the definition of rent-seeking if you consider the value of labor as only what the market will bear. By that logic, if I offer a job at $5/hour and someone takes it, any attempt by that employee to get paid above $5 is "rent-seeking".

But that brings us right back to my original point: if my choice is starvation or $5/hour, I'm going to take the $5, but that's a coercive choice. I was forced into it by the threat of death. Now explain to me how that's different from holding a gun to someone and forcing them to work? You didn't determine the value of my labor, you determined that I don't want to die.

So an attempt to increase the cost of labor (minimum wages, credentialing/protectionism) is an attempt to extract the true value of labor, even though the threat of death-by-starvation remains. Like a previous commenter said - unless we want to radically re-org our society - that threat of death is irreducible. For example, if every person was granted enough arable land to subsist off of by the state, we'd see a very different labor market.

Minimum wage laws are unrelated to unions, and prevent corporate rent seeking in welfare states.