An "insider" posted this on the PopJustice forum alleging that Britney was offered various songs from known producers but when it became evident that she wouldn't be promoting the album they decided to offer them elsewhere. They also stated that will.i.am is adamant that Britney did co-write on every song on the album, rather than simply changing a few words
"I filmed will.i.am's scrapped MTV special. He's credited as executive producer because he organised the writing and recording of half the final tracklist, and about 30 other songs that didn't make it because they were too personal and involving. It was decided Britney wasn't going to promote the album, so a lot of tracks reverted back to their producers/other artists, e.g. Leah McFall's new song, Cheryl's next single. Britney did co-wrote every track she's credited on. My interviewer bluntly asked if it was "a case of change a word, take a third", and will snapped back she wrote on almost everything."
"Whilst will.i.am didn't explain any of this, I think the logic is Britney Jean had to come in at a set cost, otherwise you have an expensive album that won't make a profit because there is no proper promotion planned and it's expected to shift a limited quantity. That means either producers accept less £££ for tracks, or they take them back.
will.i.am doesn't do stuff for the money, so I imagine he was okay with getting paid peanuts or probably nothing at all, with the guarantee his main song on the album Work Bitch was a single. Who knows? Same for David Guetta. But other producers like Dr Luke probably less likely to agree to that, especially when they know none of their music is ever going to be released as a single or even performed live.
Dr Luke would make more money turning his demo for Britney into a G.R.L or Bonnie McKee single, even with middle-of-the-road success, just due to the songwriting credits and it being a single."
They should have taken their time and release Britney Jean during her February-April break it's obvious that it still needed some work done