Lennon + Mccartney Top Songwriter Poll

Love the fact that Strummer/Jones made the top 3. Hate the fact that sell-outs like the Stones made the grade. Why not Plant/Page?My question is whether this was strictly a rock thing, or were all songwriting duos considered, and also whether it had to do with at least one of the duo being a performer. One of the great songwriting duos of all time are Burt Bacharach and Hal David, with thousands of remakes and seemingly hundreds of hits, including many classics like Alfie, A House is Not a Home, etc. Also I wondered about some of the Brill Building and Motown writers who are more obscure, but still wrote many of the world's classic songs.