Because people want to be able to do things like use their own clients of pi or opencode with LLMs they run themselves, such as the just released deepseek v4 flash 0731, not permanently tied to an Anthropic ecosystem of non-open-weight LLMs and pay forever per token.
Many people don't want to support a company pushing for regulatory capture.
It feels like the big thing they are touting here is the shared company brain. Not clear to me though, how that brain is developed when each person has their own harness. (I did only skim the docs.)
And it still has the issue of: if the agent is acting as me, then security wise it can do anything I can do. Maybe that's why they are recommending for startups.
But yes, comparison would be helpful.