...the high-explosive grenade doesn't deal anything BUT radius damage. If the script didn't calculate AoE (which you misspelled as AoO), then it would calculate the HE's DPS as zero.
But AoE weapons don't really have a limit to how many players can be affected (I guess you
could calculate how many player objects can be crammed into the area without collision overlaps, but that's not the point), so how do you determine it?
Reloading times, accuracy, special effects, even the map they're being used on and the types of players using them all factor into the actual value of a weapon in practice.
There's limitless other factors too, such as the fact that the HE grenade is one-time use, while all the other weapons aren't