The ads are obtrusive because streaming the better part of the earth's digital music collection to your doorstep at speeds that make iTunes seem like a turtle costs money. That bit may have evaded you.

Refuting your (IMO somewhat unfounded) statement on who in the US are going to love it, I'm a heavy music consumer (both in breadth and depth), and Spotify works especially well for me. In a purchase-song model, I'd be out many, many times as much per month than I am now (which also forms the disclaimer for this reply: I've been a premium subscriber for ages).