Ipod Scrobbling - Why should tracks have to be in library?

Why should the tracks be in the iTunes library in order to be scrobbled? I have a laptop and do not keep all of my music in the iTunes library at one time, therefore most of my tracks are not currently referenced, or even present on my laptop. Why would there need to be a physical location of the file to scrobble it, when just the name, length, and play date should do?

Thanks

Edit: I can see many many others have the same problem.