Because we have seen decades of organizations lying and bullshitting, they have no credibility whatsoever. There is already a lawsuit against them for rigging auctions[1], and a DoJ antitrust case [2] against them.
As long as both continue to be owned by the same parent organization, there is no trusting that they will not collude when the stakes are high enough.
Heck there is even a lawsuit of independent companies colluding to suppress wages in 2014 that [3]. One of these companies was.. Google. Even after they lost the case, the average payout was around $3800 for a class made up mostly of software engineers.
[3] https://www.seattletimes.com/business/judge-rejects-3245m-se...