The problem is, as always, insurance. Entering an unsafe building in an employment context without adequate PPE will kill off any claims for workplace injury. The pizza driver however will most likely be covered by some kind of government scheme, because him getting injured is not tied to his employment.

It's the same why store clerks are explicitly banned from intervening with thefts or fights among unruly customers. When they get injured because they willfully entered a fight, they have zero claims to make (other than trying to sue a piss poor drug addict, which is pointless) - only a security guard is insured against that.