For example, it's fine if you threw a knife at a person only for it to bounce off because it can be played off as the hilt hitting them, or the the flat side, but...
What if you threw a tremendously heavy object at a person, it doesn't hurt at all, for example.. a truck engine, which doesn't make sense at all. Right now, if you threw an engine, it'll just read...
'The HondaMitsu Bear Industrial Engine bounces off (person) and falls to the ground.'
And it wouldn't hurt at all. an engine wouldn't just 'bounce' off a person, it'll completely smash into their body and knock them onto their ass.
So, let's add a bit of realism by adding damage to a thrown object if they don't manage to catch the said heavy object, depending on the weight of an object.