How did the pay scale ever get put in place for caregivers?

This ultimately is a women's political issue. By & large most caregivers are women - whether it's done for free by family members or in a facility. Somehow it is viewed that at home caregivers is an easy job and should be done for free and out of love and familial duty. Working in a NH or AL is low pay as it too is viewed as easy to do women's work. You want change…?..get involved in electing people who will do things to support laws and programs that value the elderly and what women do as caregivers and as workers. There is legislation right now on having parity in federal wages and yes there is blowback from some members in Congress & the Senate in having this happen. Write letters, send emails, etc to your representative both federal, state & local that you as a voting taxpayer support this. When I was younger I really wasn't much of a feminist (interestingly my hubby was & is which is a source of amusement now for him) but as I have gotten older realize how important it is to do whatever to get out and support candidates (both men & women) & their programs for women. You may not exactly like the candidate 100% but really I'd rather have one who has dealt hands-on with their elderly parent or stayed up with a sick child or really has dealt with the minutia of being a caregiver than one who hasn't.

But for some reason, I will not trade it in for the world. I find joy through all of the in betweens of the day in the life of a care giver.

great answer thank you.

Is the rate pretty much by area. Those in a more fluent area charge more, those in less fluent charge less? It is a thankless job.

Some choose to quit and care for parents, then their energies burn out quickly. Siblings think everything is fine and dandy and don't offer to pay. Caregiver wants out. Because they have no job, they are trapped in a bad situation. No one wants someone who has been out of the job market for over a year, no landlord wants a tenant with no rental history.
Some keep working and hire licensed, insured professionals and pay either out of pocket or with VA Aid & Attendance or Medicaid waiver programs. This seems to work better, a bad aide is easily dismissed.
Worst of all, some hire "under the table" through an ad and end up with a scam artist with little or no training who grabs the POA and all the valuables from the house. Worse yet, they had the caregiver move in, and have no way to force them to move out without an expensive and lengthy eviction process. When they file for lost wages, they usually get paid.
The problem is that family wants the cheapest possible answer and the caregiver deserves pay appropriate to skills. This requires both sides to be realistic and willing to negotiate. Both must know the going rate in their area. Both must write down exactly what duties are for each day of the week. Both need to agree how or when the contract expires. Both need to agree on when to call 911. A handshake and a howdy doo won't work.