I think I stressed a lot on Anya wanting to fit in and Willow's anger about what happened between her and Anya in Doppelgängland, I think Anya's reasons to be a Scooby had more to do with making Xander happy than a real desire, but she learned eventually to care about others.

Of course, I'm a Xander/Spike 'shipper so I may be biased.

We all are. *g*