You may or may not be correct about 'decent' aircraft encouraging people to fly, but remember many people fly PFA aircraft or microlights.
'Decent' aircraft may give a good impression on a trial flight and encourage someone to begin to learn to fly.
I am not sure I agree with your reasoning about why people stop flying. I have seen many people pass their GFT and then stop flying. I cannot remember anyone saying to me or giving the impression that it's because of old aircraft. In nearly all cases it's due to lack of time, money or confidence.