Correct as Mr. Spenalzo may be regarding the respective quality of the tracks (especially this one!), there should be no difficulty answering the question "why?": John Lennon. If Lennon guests on your tracks you put them on the fucking album! It's Lennon! So I can't really blame Bowie and Young Americans is still a fantastic album, as is.
I agree with mr_spenalzo aswell. Who can I be now? is one of my favorites, and "John I'm Only Dancing Again" is just a wicked tune to get up and dance to, imo it's better than the, already outstanding, original.