Whilst isues of licence, ratings and medical may indeed not be causative of an accident there are a number of ramifications for the operators of the aircraft and of course the estate of the pilot and passengers who have died. The flight will be unlawful from the start which may well mean that the insurers will not pay out. This was was the case with Graham Hill, whose licence had expired and where the aircraft was actually de-registered. Colin McCray is another more recent instance where type ratings had expired, no doubt giving rise to similar problems. In the present case the owner of the aircraft could be at risk from claims where they allowed someone who seems to have been without a licence for some years to hire an aircraft. The organisation concerned might also face criminal liability. Whilst they may not have been aware of the positio they clearly should have been.
For groups, there is a clear need to keep on top of licence and medical validity to make certain that no one flys unless they are legal in every respect.
citing the fact that you would not ask to see a car drivers licence before accepting a lift ???
They have missed the point. If I lend my car to you without checking that you have a valid licence and are therefore insured I commit an offence under the Road Traffic Offenders Act!