As a teacher of mostly 3D modeling subjects, I am often asked by students if they should learn to draw. While there’s no definitive Yes or No answer to this question, I found this article at CGSociety particularly insightful.
While I certainly know a lot of successful 3D artists who can’t draw, the ones who are the fastest and most versatile are all traditional artists as well as 3D artists. Not knowing how to draw limits you in certain ways. You might still be able to have a career, but it will be more of a challenge.