a song is usually known by the famous person who sang it, not the professional songwriter who wrote it.
people who want to sing it in a karaoke setting will think of the performer, not the composer when they want to look it up.
there are singer songwriters who do their own stuff, but its just easier to catalog it all by who popularized it rather than giving a full credit listing of everyone who was involved.
and in some cases there are different covers of the same song by different people, so they will want the backing track that matches the version they know…