Because I slacked on my eris bounties and now have to get to level 3 before I can buy the item necessary to upgrade the HOP. I know HOP is a POS but it's fun to shoot for some reason.
Already had two, gave the other two Husks to my secondary characters. It's about numbers, people, not levels. Kill the lowest leveled Hive you can and just rinse, repeat til done. And if you're wondering where, Earth, rocketyard or Skywatch are two of the best places to level these guns.