Because first of all, his NAME is COOKIE monster and he likes his cookies.
Cookie monster like cookie! Om nom nom nom nom!
Cookie monster 
The cookie monster fears cookies. The cookie monster fears maddy because she is one evil cookie loving monster with 8 legs...
Who doesn't love cookies? Everyone loves cookies. Except for, of course, cookie-intolerant people don't like cookies and nor do the cookieless sphingus tribe who live in the Bahamalayan mountains.
I think that he wouldn't eat anything else, unless to drink he would probably have some milk to dip his cookies in! Cookie Monster Like Cookie!!! Om nom nom nom nom!!!
No! He Is a COOKIE monster, vegstables aren't exactly like cookies.
Cookie monster like cookie! Om nom nom nom nom!
who doesn't?! PS You sound like Cookie Monster.
Cookie monster 
The cookie monster fears cookies. The cookie monster fears maddy because she is one evil cookie loving monster with 8 legs...
Who doesn't love cookies? Everyone loves cookies. Except for, of course, cookie-intolerant people don't like cookies and nor do the cookieless sphingus tribe who live in the Bahamalayan mountains.
me want cookies!
cookie monster because most people like cookies and monsters more than cow boys
I think that he wouldn't eat anything else, unless to drink he would probably have some milk to dip his cookies in! Cookie Monster Like Cookie!!! Om nom nom nom nom!!!
ANY KIND!!! COOOOOOOOKKKKIE !!! The Cookie Monster was well known for loving a diverse range of cookies.
Cookie Monster likes cookies the most.
Cookie Monster loves all cookies but his favorite is Chocolate Chip cookies :) Hope this helps!