It's common knowledge that wasps are far more aggressive than the bees commonly found in Europe and North America. Maybe that common knowledge is wrong, but AFAICT the paper doesn't dispute that. It does admit that wasp stings are more painful, but then waves that away by arguing that most wasp species can't even sting, which is irrelevant.

Also, you're far more likely to find wasp nests (of the stinging variety) in very inconvenient places, like under an eave near your front door. This makes them far more of a potentially dangerous nuisance than bees.