The chickens are an investment and produce. A dog that kills chickens is a liability and it's nearly impossible to change that behavior once they get a taste for it. It will never be a good work dog.
I'm sure some are able to rehome them but very few.
When you live in a rural area, nobody wants a chicken-killing dog cause most them have chickens - and those that don't - have neighbors that have chickens and you don't want to be that neighbor.
If there are reasonable alternatives, please do avail yourself. When there are none, putting an animal down is best and is common practice.
