I too would like to see experienced PPL's teaching, but I don't see it happening. (By experienced I mean people who have done lots in aviation, not just the same local burger runs over and over again). My thinking is this.
Experienced PPL's will not need the money from a second job. Their first job provides a good income, otherwise they probably wouldn't be able to get good quality experience as a PPL. So money will not be a motivating factor.
So they must want to do it for the flying. The trouble is most experienced PPL's will have little interest in flying around the circuit, or doing the (relatively local) cross countries that are involved in PPL training. So the flying will not be much of a motivating factor either.
That leaves the 'reward' of seeing someone develop and learn. Perhaps there are enough people for whom this is sufficent reward to give up their weekends/evenings, but I doubt it.
I imagine an experienced PPL would be happy helping newly qualified PPL's expand their experience and taking on bigger challenges, but not so trilled about goind around endless circuits.
dp