Open your browser. Type google.com in the address bar. Now type Liszt scores in the search bar. "Category:Liszt, Franz" is listed 9th on the first page. Now type Liszt sheet music in the search bar. Where is "Category:Liszt, Franz" in the latter search results? Nowhere on the first 20 pages...
"Sheet music" should be a keyword on IMSLP. Scores are very often just refered as "sheet music" by the music community on the internet. Even I personally searched after "sheet music" when I wanted to find a score in those days. Please try searching after "beethoven", "mozart" and "chopin" to, you will see the same pattern.
Recent observation...
Moderator: kcleung