archers/hunters with ele's in their weapon are PvP'ers. in PvP, when you have targetted some1 another from the opposite faction, you can see their buffs, and so the elemental buff. By this, it's not hard to have an opposite elemental top to get less dmg from that person. Ofc that person can switch from elemental, but as said it requires a lot SP to switch while switching tops doesn't need SP
people is using ele skills for PvE. and when they've hit end lvl, most of them buy an reskill stone to invest in another and PvP skills. By this, he/she can get ele lapis for the weapon.
don't forget that the ele skill will overrule the ele lapis in the weapon, even if the skill is lvl1 ele while you have ele2 in your weapon.
furthermore, some PvP'ers are buying the ele skills too, but only to lvl2 with a purpose to mislead the opponent. before attacking, a rightmouseclick on the elemental buff will disappear it, so you've a strong ele against his ele top because he's taken that ele to counter your ele buff