Because you can't really draw all that well.
My first commercial art gig was at the age of fifteen and my employer at the ice cream shop was going to open a new rib joint, and he asked me to design a logo. So I drew a frog in a cowboy hat riding a pig. The place was called "Rib It!"
Since then, I've worked with all types and sizes of companies to help them create identities all their own. Let me find your frog in a cowboy hat riding a pig.