How much do you care about the beauty of UI?

I am seeing people try to build nice interfaces, I agree they look pretty and build it if you can for sure. However, I am from a generation that used gray forms on all applications and it was not that bad considering how useful and fast the applications back then. So, I am not sure how important UI in the sales as long as UX is good and it gets the job done. What do you think about it?