Why would an accomplished musician take up singing when t…

https://www.musical-u.com/learn/isnt-it-time-you-learned-to-sing/
Why would an accomplished musician take up singing when they were already succeeding as an instrumentalist? What makes singing so important for musicians and so vital for good musicianship? And why would you take lessons rather than just trying to teach yourself to sing?
https://www.musical-u.com/learn/isnt-it-time-you-learned-to-sing/