> There is no law of nature that says we need to pay people with the jobs that are worst for their health the worst and give them no respect or acknowledgement.
It's not a law of nature, no; but it is a law of human psychology/economics.
The jobs that nobody wants to do aren't competed for—there are always plenty of such jobs to go around. Therefore, there's nobody kept out of the field. Therefore, the field doesn't ever build any social cachet of exclusivity. And that's a problem, because exclusivity is a prerequisite for the general halo-effect of respect that a field's members can earn.
Example: doctors must know a lot to do their jobs—but we wouldn't default to thinking of doctors as "knowing a lot" if anyone could be one without proving that they know a lot. We'd distinguish "well-trained doctors" from "badly-trained doctors" and we'd certainly give some props to the well-trained ones, but "being a doctor" would no longer command respect on its own. It'd be like... being a programmer, for instance.
That general halo-effect of respect is essentially what drives the ability of a class of workers to collectively bargain—it's what makes the other side of the negotiation treat them seriously. They know that people that are respected by society have a voice in that society, that they can use to denounce bad employers. So they actually sit down and bargain, rather than just firing all their old employees and getting a new batch.
Microecon says that jobs with more employer-demand than employee-supply should pay more, because employers must compete for employees. But because of this failure-of-negotiating-power, this doesn't happen; all the employers effectively are in implicit collusion to keep the wages of such employees down, by just not even taking seriously the idea that they should be competing for such employees. (It's kind of the same effect as employers "implicitly colluding" to fail to compete for talented female employees—but instead of being driven by employers' biases about demographics, it's driven by employers' biases about the assumed social-power that an employee must have if they are willing to take a particular job.)
But to get the members of the field to be respected—rather than just sympathized with (see e.g. sanitation workers—they have "hard jobs", everyone knows this, and people try to not make their lives harder than it is—but being one still doesn't make you any more likely to be listened to at a town council meeting), the field must first become more exclusive. That can work for fields where most of the work occurs in one place—see Hollywood and their actors' and writers' guilds. But if the work is distributed (like with community moderators)—how is the exclusivity going to happen?