Because he's God?
When an adult falls and skins their knee, it's a momentary inconvenience, when a toddler does it they suffer.
A teenager gets their heart broken, their parents try to comfort them, but the teenager is suffering.
A loved one dies, we suffer.
Each of us has many events in our lives where we were suffering, in nearly all cases we can look back on the event and see that it was nothing, but in the moment we experienced genuine suffering.