You are also making the very wrong assumption that people who get paid ie CPL holders with an FI ticket do a worse job than a PPL FI would.
No, I am seriously not. My point was that whether an instructor gets paid or not every instructor is (or should be) trained to the same standard. That is what the FIs qualification, as any qualification, seeks to achieve.
Why should you get paid for any job? Just because I enjoy flying doesn't change anything. I'm lucky because I enjoy my job. I'll be damned if anyone is going to tell me that just because a job is "fun" you shouldn't recieve any pay for it.
And
Supply and demand controls the market
You see this is the point. You have chosen to do something a lot of people will do for little or no pay. Most jobs involve significant elements of grind and that is why there is a shortage of people willing to work for nothing. Moreover most jobs require a degree of continuity - for example, you don’t want to talk to a different solicitor every time you ‘phone. However many think that they can do a bit of teaching when it suites them (while the normal day job pays the mortgauge) and they are probably right. Does the student care if you are there when he ‘phones up on a Friday - almost certainly not, as long as you are there for his lessons every Wednesday. We pay people because in many cases it causes them to turn up in the morning and spend at least some of their time doing something they would prefer not to be doing!
My best instructor ran a bedroom furniture shop - it provided him with a good income, he taught three afternoons a week, his students knew when he was on “duty” and he was never short of a booking. He was hugely enthusiastic about his flying (perhaps the more so because only teaching three days a week he looked forward to each teaching day) and he was very good at what he did. As it happens he was paid.
If I started a club which invested substantially in new aircraft and was staffed by PPL FIs or whatever new animal EASA might throw up I would probably get plenty of volunteers and I might even run a successful business. Alternatively I might find by paying my instructors they were more committed and turned up more reliably. I wonder.