If by that, you mean the US business model, that's where I land. The corporations came in and bought "all" the doctors. For most PCP's, it makes sense to work for a corporate-owned practice. The corporations do what they do best...sweeten the deal to make their offer just slightly better than the alternative. Then, once in control, put the screws to their employees to be "more efficient". So now the practice has 120% of their former patient load, and the earliest appointment is in 4 months. It's driven by insurance networks. In a geography there are a certain number of practices taking certain flavors of insurance. In that same geography, there are more patients that hold those insurance types than can be managed by the available in-network doctors. They're selling more doctors than they have.
So that goes to the question of paying the fee. It's like paying the DoorDash driver a tip in advance; they won't take your order unless you pre-tip. I don't like the business model, but I certainly won't be using an over-booked corporate slave PCP either (once I'm on traditional Medicare).
One thing I worry about in selecting to pre-tip my PCP is that the corporate types aren't going to let these renegade doctors have an easy time taking business away from the corporate monster. So question number one for any doctor charging a fee would be "who owns the practice?" If it's big business, and the majority are, there's probably little value in paying to play in that environment because they're still answering to the corporate overlords. If it's a set of individuals, then I'd probably play so I'd get consistent access.