system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why a pancreas transplant does not cure Diabetes?
gpt
In the case of type 1 diabetes, you have the ongoing autoimmunity to deal with.  The reason someone with T1D has a damaged pancreas to begin with is their immune system wiped it out.  If you put a new pancreas in, the immune system will just wipe it out as well.  (This would be something like trying to build a new house on top of the flames that burned up your old house.)

We can use anti-rejection drugs like they do for other transplant patients, but generally living with T1D is preferred to living with transplant drugs. 

In the case of type 2 diabetes, the problem (generally) is insulin resistance, so a pancreatic  transplant wouldn't help much.  The issue is that the cells don't respond well to insulin, not that there isn't insulin being made.