It kind of depends on the network. For a real owned and operated HMO where every provider in the network buildings and offices is an employee of the network (or under contract as a network provider), in-network only (for non-emergency services) makes a lot of sense to control costs, make staffing predictable, ensure consistency of care, etc. As an insured, you go to one building and get everything taken covered. If you want to go out of network for something, you need a good reason or be willing to pay for the whole thing.

When it's a third party HMO network and you've got stuff like a medical office where only some doctors are in network and others aren't, so if your doctor is behind or out sick and you're offered to see another doctor in the interest of time and then you've seen an out of network doctor, that's a totally different deal. Then you've got things like in-office X-ray analyzed by an off-site radiologist whose identity and network status wasn't known before hand.

I'd like to see non-emergency medicine take up the same kind of quoting requirements as auto repair. You can't always stop a procedure to update the quote, so provide several quotes for the likely outcomes.