Its also because big ass herbivores are actually really dangerous.
Sharks don't actually like the taste of humans because we're a little too lean. So they won't actively hunt you unless they're starving. There's only really one reason why a shark is out to get you. There's many reasons a herbivore will mess you up.
A big herbivore will fk you up because he's having a bad day and you got too close. Or its mating season and everyone is potential competition.
Or they mistook you for a predator cause of their poor eyesight.
Or a bird flew away nearby and one of them got startled and now you're in a path of a stampede.
Sharks may also bite you by accident, because they mistake you for a seal.
How dangerous a bull is also depends on his age. While getting older he will start to lose the fear/respect for humans. This will get to a point where being alone with him is a literal death sentence.