In "Him" in Season 7, Anya had already robbed a bank. It would have been fitting for them to have used that stash (which is never used in Season 7) because they bank they owe it to is at the bottom of the pit that used to be Sunnydale by then.Imo It did seem bloody weird to totally ignore Spikes character as he played such an integral part of season 7, but then thats what I hated about season 8 was that you never did see how they got from the end of season 7 to the beginning of 8. The whole bank robbing bit for example.
And I strongly doubt they ignored Spike for the reasons your citing. I think It was more because they felt he didn't fit in the story they were telling.