So tell me, why is a raven like a writing desk?

There is no answer

They both are easy to stick gum to

I haven't the slightest idea...

Not a thing~

Poe wrote on both.

The question was originally designed with no answer, since it was an illogical question there was never meant to be a sensible answer. The entire point of the riddle is that it has no answer.  However so many people kept asking, that the author gave an answer in the preface of a later book:

 

“Because it can produce a few notes, tho they are very flat; and it is nevar put with the wrong end in front!” 

Caroll's pun of spelling Never like Nevar, which is "Raven" backwards was unfortunately lost to the red pen of a proofreader, confusing the issue of the riddle even further.