Well since your avatar is holding up three fingers I see why....
EDIT: And the reason we do this is because over half the people in our groups are NOT quick at math, like at all!!!
Who said it's solving a problem?
If it isn't solving a problem, why consider it at all?
If there was a campaign where weapons dealt fixed damage, e.g a dagger did 3+STR/DEX points of damage, a greatsword did 7+STR, etc. Would you be happy? Would it take away from the fun of rolling damage for you? Or would you be content if it sped up play?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.