Do you think that sketching is necessary?

Tweet

Like title says.. Is hand drawing a requirement to become a graphical designer? What do you think? I dropped my university studies because a teacher told me ''If you don't sketch/draw, then quit'', i just stood there, cold.. A week later i dropped.. I've been doing design for 2-3 years now, never made a sketch on pencil, i just let the piece flow and keep adding stuff, i consider this adds fun to the actual working piece, and yet you never know what to expect of the final product.. Don't know why but i just like doing it this way, enjoy it.. My style focuses on photomanipulation, anyone here does this kind of work too? Just want to know some experiences that you had with clients/teachers/assignments, some clients NEED a sketch or they just won't buy the idea.. Atleast here in my country is like that u.u.. Ps: Sorry, my english is kind of bad..