Here's how I see it anyway.
Everything was based around the hit single, which was everybody's bread and butter and needed to be delivered at least three or four times a year in a career that was only going to continue if you could keep on delivering chart hits.
And it was an incredibly competitive market place. With the likes of The Beatles and the Stones sitting on the top of the heap, and a second tier (we're specifically talking the British market here) made up of the likes of The Who, The Kinks, The Animals, The Hollies, The Yardbirds and Manfred Mann, all of whom were delivering pretty consistently over the time frame we're looking at, it wasn't going to be an easy nut to crack.
Which, of course, explains the number of one hit wonders who shot to temporary prominence. It wasn't easy to deliver something that would make the audience stop, sit up and take notice, and having done it once it wasn't always easy to do it again.
In that environment, something like the Small Faces third single Sha-La-La-La-Lee, written by Kenny Lynch and Mort Shuman, with its Picked her up on a Friday night opening line was a natural fit. The band might have hated the song, and Lynch may have been a relative lightweight, but Shuman was coming off the New York-based writing partnership with Doc Pomus that produced Teenager in Love, Save The Last Dance For Me, Little Sister, His Latest Flame, Viva Las Vegas and Sweets for my Sweet.
Their August 1965 debut single Whatcha Gonna Do About It (tune by Steve Marriott and Ronnie Lane, based on Solomon Burke's Everybody Needs Somebody to Love, words by Ian Samwell) had charted respectably, the second, I've Got Mine, also written by singer Steve Marriott and bass player Ronnie Lane, had tanked after it was released in November, so it was a case of outside help or, potentially, the scrap heap when manager Don Arden was looking for a follow up in January 1966.