That said, the Culture does seem like it would be a nice place to live, over all.
Banks himself was distinctly anti-capitalist.
Take the current political situation in the US. Trump would love for everybody to blindly obey him. His autocratic goals are frustrated by the fact that government is made up of people who are able to resist the government they are part of if they believe it's going wrong. Without those people, Trump could count on the obedience of the literal machinery of government. Having people involved can be an extra layer of protection against abuse.
':-|
I think his point was that even if you live in a post-scarcity anarcho-communist society where everyone is live and let live, the rest of the universe isn't an occasionally you need headbangers.