Why Doesn't the Kidney Transplant Waiting List Reflect the Missing 500,000?

This is a follow-up to the last post found here.
I think there are several possible components which together combine to give at least a partial explanation as to where are the missing 500,000 people with ESRD who are not on the kidney-transplant-waiting-list.
I think that a critical but correctable component of the problem is that the supply of kidneys that become available annually are so miniscule compared to the demand for kidneys, that patients and their physicians often face the grim reality that (under the current manner in which UNOS appropriates organs) their chances of obtaining a kidney are so slight that they make the sad (but often economically rational decision) not to undergo the financial, physical, and emotional burden and trauma of living with the constant anxiety of waiting for an organ that may never come so they just fore-go the process altogether and survive on maintenance dialysis.
This problem can be at least partially ameliorated by expanding the supply of kidneys available for transplantation - like by increasing the supply of live donors! (Another more long term approach to the problem is to screen high risk populations for high blood pressure [like African Americans, people with diabetes, etv.] before they present with symptoms of ESRD so that their blood pressures can be controlled and their kidneys continue to function at an acceptable level. This would decrease the amount of kidneys demanded on the transplant list.)
Some other components that may explain the missing 500,000 people from the kidney transplant waiting list may include:
1. Some people are so sick they would probably never live through the procedure so they don't bother trying to get on the waiting list.
2. Geographically, some people are very distant from a transplant center so they might not be able to get to the transplant center in time to get the organ so they don't bother signing up (but keep in mind that the time sensitive component of transplantation goes away with live-donor-donations).
3. Some people cannot afford the costs involved in the transplant. For instance, they might be denied a spot on the transplant list if the transplant center thinks they may not be able to afford the anti-rejection medication needed to elongate the lifespan of the organ.