There are several other reasons as to why Michael Jackson recorded certain songs but he did not include them on his albums.
Keep in mind that he was primarily a hits-oriented artist, which means that he wanted to include potential hits on his albums.
So, in the end, the selection of songs for the final track list came down mainly to that criterion.
Or, on other instances, certain songs could not be included on an album due to contractual/royalties disputes.
For example, although he recorded the 'Behind The Mask' cover song by even adding additional lyrical and melodic elements to it, royalties disputes with Yellow Magic Orchestra's management did not allow the inclusion of it on his 'Thriller' album.