Can someone explain something to me?

I don't understand those people who start flaming you like mad simply over not completing a jungle item. Yes, jungle items can be gold efficient, but you aren't required to finish them. I know a lot of shaco players for example not finishing their jungle item. There are some champions I complete my jungle item on and some I don't. My last game for example, I had a guy who got auto filled into adc and rather than play or ask to change rolls, he goes singed adc. I had been invaded twice early by the enemy jungler without help from my laners. Despite this, I still ganked a couple of times in lane and got us first dragon. Yet, I start getting flamed by singed for not upgrading my machete. I don't understand this, I wasn't feeding either because at that point I only had 1 death. Just kept calling me a troll, trying to give us, etc. Can anyone explain to me what was going on?