I feel like Krugs are designed to waste your time...
Yea, you get a ton of gold if you manage to kill the entire camp, but the amount of time you need to invest to do this isn't worth it most of the time. In the amount of time you spend trying to clear this, you're missing out on a teamfight, helping your team push, securing an objective, or something else much more important. Not to mention the fact that the small ones are REALLY difficult to target and often spawn in really annoying locations sometimes (like on the other side of the wall. They should make krugs less tanky or reduce their damage. In their current state they're just not worth your time.