Why didn't Spike go back to Buffy?

I haven't seen all the エンジェル Seasons, so bare with me, but I think it was something like:
Spike was brought back because he actually died too soon and he had a greater purpose, he still had a destiny to fulfill but it required him to stay in LA, so he did.

Because he didn't know whether Buffy would get back together with him.

He was all self-conscious and didn't know whether Buffy would want him back. Plus there was that whole incorporial thing for a while, and after having to stay around エンジェル for a while I think he got attatched to the whole 'being a hero' and 'saving the world' thing with Angel. Plus when he and エンジェル go to Italy and Buffy is "supposedly" with The Immortal, they both get pretty broody. Double brooding.