I don't want to speak for anyone else, but dialysis involves putting a huge catheter in the patient's neck. Then the patient is hooked up to a machine and has to sit still for about 3-6 hours while their blood is processed. Since cats are so small, at any given time during the procedure they are missing a significant amount of their blood (I think our machine holds 67mL minimum). So the procedure itself is rough and has to be done every 1-2 days. Besides that, the patient is uremic most of the time unless you are dialyzing aggressively every day (at $800 a pop) and they feel really awful, plus they get the uremic complications like uremic lung, GI ulceration, etc. If the patient is anuric they can't drink and they get fluid overloaded just from fat breakdown and that makes it hard for them to breathe. So basically, it's really unpleasant for the cat and it is not something that is sustainable long term either from a quality of life or a financial perspective.
I think there is certainly a place for dialysis in situations like acute ethylene glycol toxicity where it's a one-time treatment that saves their life and allows them a normal life expectancy. I think it is pretty gray territory when you're maintaining an animal on dialysis in hopes of a transplant or that they will regain the ability to urinate post acute kidney injury. I think it's definitely unethical to maintain a chronic renal failure animal on dialysis long term because it is so stressful on the animal and in between they will be feeling awful.
Curious to see what cdndvm has to say