This is a concept that I feel the need to explain since it seems that even at high gold, low platinum Elo it isn't understood.
It is not the Jungler's job to stop you from feeding. You need to understand that if you die twice before he can even do one full clear, it's extremely difficult to gank for you now. The enemy laner is going to have a huge stat advantage. Tank junglers aren't going to be able to withstand damage from a carry who gets fed early. Assassin junglers aren't going to be able to burst a champion who has three levels advantage on them. With every kill that you feed over it makes it THAT much harder to gank for you.
Back. Up. Should the jungler help a losing lane? Sometimes, sure. However, if your laner is fed, it's going to require more set-up from the jungler to succeed.
"Set up for a gank? It takes 10 seconds, just get in there and do it, you just suck" - (Actual comment I've seen today)
Yes, set up. If the enemy has vision and can see the jungler coming, they can evade the gank mush easier. Vision control is required to some degree. Scuttles, vision cones, control wards, sweepers, regular wards. If the top laner is begging for a gank, but the enemy laner has a control ward in the bush and the entire topside of the map is dark, that is an extremely dangerous gank and won't likely be possible if the enemy laner is good. (which, he should be, right? If the enemy isn't good, that means someone who isn't good getting fed, which doesn't look good on the person giving over kills, does it?).
If the enemy jungler is MIA, this also makes it difficult, ESPECIALLY if the enemy jungler is also fed off of the laner's deaths. You know what would make the situation far worse? You desperately needing a gank because your laner is fed, only to have a counter-gank occur and both you and the jungler die. If the jungler has yet to die, that's a significant chunk of gold that he is worth compared to someone who has died two or three times. Not to mention with two laners in a solo lane, or three people bot unopposed, that all but guarantees that the turret is going to fall along with an objective (Rift, dragon).
Thirdly, the enemy laner needs to be pushed in. If you need a gank, stop pushing the wave. Did you push the wave anyway? Miss some CS. Ganking a fed champion is hard. Tower diving a fed champion is nearly impossible. Middle of the wave likely won't work either, especially if they have any kind of mobility or their flash is up.
Gank's require set-up. This isn't arguable. Sometimes they set-up themselves for the most part, but relying purely on the enemy being in an opportunistic spot and not paying adequate attention is a poor strategy. A strategy that relies solely on your opponent sucking is not a recipe for success. Finding the right angle, getting vision, planning a route, having the cooldowns up; these things take time.
If the enemy laner has a full damage item to your junglers bami cinder, your jungler will not be tanky. They will be bursted. If your laner has a Black Cleaver to your Jungler's fiendish codex and mana crystal, your laner isn't going to be bursted.
It is YOUR job to ward. It is YOUR job to play it safe when you fall behind. It is YOUR job to cut your losses and look for opportunities to help your team and stop the bleeding. Your jungler is not a god. He is not your savior. He is not your babysitter. He does not have to gank you at all. It is not anyone's fault but your own if you feed.