"On the other hand, a services business might not be ideal for a hyperbrain, since clients naturally care about the work you’re doing for them now, rather than the work you did for other clients in the past."
Probably you're right that services aren't good for "hyperbrains", but I don't think that's the cause. In a services business there is something you build, and that's your reputation. As your reputation grows, your prizes grow too, and also you get to be pickier about the kind of work you choose. So that's the backlog of the services business.
So while you're right that a backlog is useful and needed, it can be derived from the services business too.
Absolutely, and I know some hyperbrains running services businesses, but they all complain about it. The problem in the case of the services business is that your backlist can evaporate quite quickly if you screw up in the future. It's not really lasting value, because if you're on a down cycle when the client needs you, they'll quickly change their mind and your reputation will go back down.
My few successes in my time working in services came about when I was poorly supervised, and was able to rigorously control the eventual output.
In contrast, working on projects that other people controlled was often an exercise in frustration and compromise.