Here's the problem with poor social skills: you put a low ceiling over your head. If you can't interact well with your co-workers, managers, and others, you won't get very far in your company.

You are free to be an asshole. But don't complain about the corners you put yourself into because of the choices you made.

"Kindness" is a pretty vague term. I think "empathy" might better suit your question.

It's rather difficult for some types of people to learn, especially if they're not exactly wired for that or their cultural or familial background didn't put much emphasis on it.

In the programming profession, it's not particularly useful when you primarily deal with computers (computers just don't care).