Replace catalytic converters new one did not come with heat shields old ones don’t fit do you have to install them 2010 Subaru Forester
If they were absolutely necessary the new cats would have included them.
Some vehicles come off the assembly without heat shields for the cat.
If you live where fires are prevalent like California, you might want a heat shield. In any case, without the heat shield, don’t park on brown grass.
I would suspect that depending upon the grass a car could catch on fire shields or not shields. That happened with an OK state trooper not many years ago after he chased a suspect into a field and bailed out for a foot pursuit.
Five minutes later the patrol car was going up in flames and became a total loss.