A lot of songwriters punt their songs to big companies who have a stable of singers and bands and top class recording facilities and quality session musicians so it's unsurprising that from time to time pop musicians pick up a good song.
What gets me more is when quality songwriters sell out as happened with Randy Newman who I loved in the seventies, especially the amazing and contentious political satire he was churning out on albums like Good Old Boys and the borderline politically incorrect humourous stuff like "Short People" which was not about physical height despite the court cases. This is the guy who wrote Mama Told Me Not to Come and You Can Leave Your Hat on as well as a string of hits for other artists from the 60s onwards (Dusty Springfield, Wilson Pickett, Manfred Mann, Peggy Lee, Alan Price, UB40 etc)
Then he realised that his style is perfect for the movies and by the late eighties had become a mainstream Hollywood score writer and churned out sugary cack for breakfast to boost the coffers. Never imagined he would waste his immense talents on Toy Story, Monsters Inc, A Bug's Life etc. but I guess that's where the money was at.
My kids love taking the piss when I mention that I like his early stuff - but they are the ones who cringe when they realise a song they like is by the guy who wrote the soundtrack for Meet the Fockers.