It's because there are additional regulatory requirements on businesses that have disproportionate market influence.
Promoting your own services in general is fine. But when a huge, huge majority of the market uses your service for discovery, your decision to promote your own services over competitors' damages competition in the market — users end up with less choice in practice, even though they could theoretically switch to another service.
Those rules exist to try and prevent this sort of abuse happening.
Promoting your own services in general is fine. But when a huge, huge majority of the market uses your service for discovery, your decision to promote your own services over competitors' damages competition in the market — users end up with less choice in practice, even though they could theoretically switch to another service.
Those rules exist to try and prevent this sort of abuse happening.