A number one hit doesn’t mean it’s the most creative song. It doesn’t mean it’s the song with the deepest meaning. It doesn’t mean that it’s the best use of the musician’s talent. It simply means it’s the most popular.
An album filled with all of the songs that made it to the number 1 spot on the Billboard charts is an album that is meant to be the most appealing to the most people. Broad appeal.
For artists who have made a dozen albums, there are many more ways you could create new albums from their past works. You could make an album with positive vibe songs only, or flip that for negative vibes. You could create an album for only their songs involving themes of love. You could create an album of all the songs under a certain length.
You don’t see many anthology albums outside of “Greatest Hits” or “Number 1’s” because no one is sure if they will appeal to many people. Mashing together all the best hits seems like it would do the best, but it’s not actually a certainty that is true. What if those downbeat songs weren’t popular on the other albums because they were “moodkillers” in the middle of an otherwise upbeat album. Yet, mashing them all together means the whole album is for someone in that mood. Many people might be looking for exactly that.
There are plenty of ways to package things. To rework the past and put together in a way that is palatable to a new audience. Often it takes someone willing to do something that might not work to see it.