There is no easy answer to this question, as it depends on the mentality of each provider. Some don't want to play the "insurance game" and choose to be OON, others want to get as many patients as they can, and contract with every insurance that they can. Here is what I have found over the years...most PATIENTS want to know that they are seeing a contracted provider with their insurance. And you have to be honest with them when they call, and ask if your office/provider is in network. If your provider isn't, you will lose patients, because they will say thanks, but no thanks, and move on to a provider who is is contracted with their plan.
Right now, I am dealing with contracting a provider with all insurances our office is contracted with. Unfortunately, there is one insurance in our area that is no longer accepting providers within our specialty. (Humana, Podiatry). So while two of the docs in our practice are grandfathered in with Humana, the newest one can't get into Humana(which is fine by me, I HATE Humana). So when a patient with Humana calls, we have to explain that while they can schedule with two of our providers, and that will be a few weeks for an appointment, they can also schedule with the new provider immediately, but it will be out of network. 9 times out of 10, the patient says they will call around for another appointment, that will be sooner, with an in-network provider. And I completely understand why. Who wants to see an OON provider when they can see one who is in-network?
There are situations where not being contracted doesn't matter to potential patients, and not being contracted doesn't matter to the provider. But they are not the norm. It depends on the provider specialty/financial situation/length of practice, and the patient demographic in your area.