Is the skill of icon design required for a good UI/UX designer?

I sincerely apologize if this question is way too amateurish but I really could use some opinions on this.

I know there are places and ways to get icons online, but a) those options at times are pretty pricey, b) it's not always easy or possible to find icons in one style that would fit a given project, and c) I also know that some clients in their briefs request custom icons to be made. So is it worth it to invest time in learning icon design, especially in the beginning? And what UI/UX designers usually do? Do they design their icons themselves, or do they buy them, outsource, etc?