They do drop loot those engrams are loot. At the end you also get loot too my guess is that the rates you want well obviously have a low chance because of they dropped often the game would be too easy and not really a challenge. Although you do have a legitimate concern I feel that it's fine the way it is. It does have a loot system just one that isn't like all the other games out there and I am fine with that because some change is good a new way to look at things is always refreshing rather than a traditional loot system