There's a trend for releasing "best" albums recently. I saw it on the news and music industry experts say that it's because the turnover for musicians & artists is much quicker than it used to be. Popularity now is much more fleeting for newer singers and record companies often release best albums for a few reasons: 1) more money in a shorter amount of time, 2) stores prefer it [they'd rather stock a compilation album of popular singles than every album someone releases, it saves space], 3) it's an easy way to get new fans who want to sample an artist's most popular work, possibly leading to buying a full original album.