[indy]

They only store a catalog of the most popular songs. (Where 'most popular' is determined by your geographical location). This catalog is periodically updated.

[neves]

Isn't the use case to find obscure music? Weird to have just popular ones. To "discover" a top 10 hit I can just ask someone nearby.

[mjlee]

I think the Pareto principal kicks in hard here. If it stores the top 20,000 songs as the other comments suggest then I expect that would include the vast majority of music you’d come across.

[jlardinois]

Not necessarily. Everything is "obscure" to you the first time you hear it.

[neinzero]

Top 10, yes, but not top 10,000.