What is wrong with acquiring a skill that is completely unlike what you normally do. It's enriching experience and challenges you mentally more than learning so

What is wrong with acquiring a skill that is completely unlike what you normally do. It's enriching experience and challenges you mentally more than learning something that is very much like what you already know/do. No one is saying that just because you learn to program you will be seeking to do it professionally. I think mayor of New York knows better than to quit his post and start seeking some janitorial programming position.