Personally I don't care about being paid for unused vacation days. I just want my vacation. And I don't want to have to use it all for Christmas. (Some employers I've worked for give you a week or two for Christmas automatically, some make you use your allocated days.)

I think it makes sense to pay out for vacation days one could have taken but didn't when they quit or get laid off. I'm not sure it makes sense to pay for vacation not taken in previous years, but maybe.