Tyre Pressures (I know, I know...)

So I have been thinking why do manufacturers of tyres and bikes recommend 36 front 42 rear if when I go to the track I can use 30/30 without a problem? Is it just about longevity? Why else would I want to run 42psi in the rear tyre scratching around the twisties or blasting up the freeway?

part of it is longevity, part of it is low speed grip, i believe

The lower the pressure the more heat you can generate, but offcourse at the track you can generate too much heat & have the tyre go off at the track in winter I have gone as low as 25psi cold with solo tyres & sidecar tyres 15 psi gets real squirmy chasing heat
Road tyres are constructed differently in many ways