Because unlike other MMOs where blue is the same for everyone, it is more about the stats on that piece of gear than its grade.
Some archers tend to use lv58 green pants for example.
I'm not sure if there is a mechanic behind it but the green drop often has better average stats than the blue one.
So with 2 to 3 drops in 10mins that's just for the dice roll of getting a blue, you still have the second stage of RNG which is the stats.
Also, the fact that the base stats (def, m.def, evasion) for blue gears is the same even on a different blue set of the same level is strange to me. Why isn't one evasion favored while other is def, m.def? It sounds simple but that literally allows player to choose what build they want to make just like an action RPG game. That also puts a different values on these blues of the same level
When I started farming DDF, it was exciting to get a drop whatever it was. Now, not so much. Because I know that it will most likely have stats that aren't desirable.
Which makes blue gear not really that special.