Before anything else, I agree question of type "[link/name of piece or song] sounds/is/looks/whatevers cool, search the sheet music for me" should be closed. Nowadays, with the internet and advanced search engines, it is very easy to find sheet music for most pieces.
But, I think manuscripts of classical music should be an exception. (Specifically manuscripts. Published editions are exactly as easy to find, per the above reasoning.)
Firstly, the manuscript is for a large part of classical music the definitive version, which allows the performer to get as close to the original intent of the composer as possible.
Secondly, although lots of editions advertise with being "Urtext" (meaning they adhere to the manuscript), in many cases, just by typesetting, valuable information is lost.
Thirdly, not all pieces have been published satisfactorily. Of some pieces, only edited or low quality publications have been made.
Lastly, I'd like to note requesting copies of manuscripts is standard practice in the classical music world.
P.S. In case you are wondering why I brought this up: https://music.stackexchange.com/questions/31834/where-is-the-manuscript-of-escenas-romanticas-by-granados