That's probably part of it, but also, to the extent that they were bona fide contractors, the cost of actually policing them to prevent direct contracting with and referrals from the people they were matched with through Homejoy was probably a problem.
Contracts may theoretically restrict this behavior, but actually policing them is non-trivial.
Yeah, I think that's part of the general cost breakdown here: something like house cleaning is already very competitive so there's a pretty narrow range where you can convince workers to give you a cut without pricing the service out of consideration. Successful attempts to do that rely on high volume, which is completely incompatible with the kind of things you mention or even basic customer service and quality review.
Contracts may theoretically restrict this behavior, but actually policing them is non-trivial.