[eyko]

I can imagine dragging smaller asteroids and letting them "drop" into earth (e.g. attach massive parachutes and then guide them to land on some mining site. Totally sci-fi but I still find it less so than the moon. The reason I don't imagine robots mining the moon is that minerals, as you say, are not readily on the surface, nor is the moon mainly made up of a specific mineral.

[mcv]

I once heard that the one thing we might mine on the moon is He3, once/if we get to that level of fusion power. There's apparently a lot of it, and it's right at the surface.

But the advantage of asteroids is that everything is at the surface.