Demand isn't necessarily high.
For example a few years ago I fell over and broke my collarbone.
I was referred to the fracture clinic where the doctors opening remark was, "We'll get you in and operate on it as soon as we can".
My answer (because I am a coward!), "Hold on a minute...What happens if you don't operate?"
The barber of Southampton General Hospital said "Oh it'll get better on it's own".
So thats what happened.
A month later I went back again to see them at their request, and a different dr said, yep, all healing up nicely. If I'd had it operated on it would have been a 3 hour job, in hospital for a week after, and off work for at least 8 weeks.
I was back at work after 4. So, 3 hour op? God only knows what that would cost. A week in stalag SGH, how much was that going to be? 8 weeks off work, OK, costs my employers more than HMG, but SSP would have gone to work so thats another couple of £100 wasted.
Obviously I didn't need an operation, so why did they try and talk me into it? I am cynical, very cynical, so my opinion it's justifying their own existence. next obvious point is how many more unnecessary operations are happening?