she thought the songs were not good enough and she wanted to revisit them for later use. some of the songs are rather personal, which is also why she did not want them to be heard just yet. most of the songs were just put on hold.
If you know/don't mind saying, did Amy start to record/finish her 3rd studio album? I know you've said she recorded 20 songs (which is already a lot to take in coz i swear i almost had a heart attack.. i'm only 16 - that can't be good) Cause on her twitter she mentioned a few songs saying they were 'on the next one' :-D