Why did it take so long to release?

This is just a hunch on my part, but I suspect Albert Maysles didn't feel like he really had enough of substance. I sort of feel that way, but as a die-hard Paul fan, I still found this interesting, if a bit meandering. There's a partial explanation for the delay here, but you have to read between the lines ("for various reasons"):
http://www.sfgate.com/default/article/Paul-McCartney-The-Love-We-Make- youthful-zeal-2403629.php