It's one thing to sell your services at a loss while you're growing. In the home-cleaning business, though, there will never be a shortage of undocumented immigrants willing to work for less than minimum wage, quite possibly at a higher quality level. There would be no way to ever raise prices to fully cover costs without immediately losing out to that competition.

If anything, the incumbents are better positioned to arbitrage the law/regulations in this case. An online service like this leaves a paper trail, which makes it much harder to use the "shortcuts" common in the cleaning industry: use of undocumented immigrants, underreporting of taxable income, etc. Much easier to do that in a pure cash business with informal booking.

Contracts may theoretically restrict this behavior, but actually policing them is non-trivial.