it's not at all that difficult to pick up the ball and keep it rolling with a PC. It's not. It's a ROLE PLAYING GAME for pete's sake. If people are having problems coming up with new hooks especially when there are other hopefully still alive PC's at the table to hook into? Then there's a problem.
I'm sorry I dont think that rust monsters are a deal breaker. For me as a GM if I throw a rust monster at my players characters and someone's valued weapon or armor gets hosed, it's just an opportunity for them to get some newer, cooler weapons and armor. The trick is not to be a dick about I guess. If your players know that you're not out to screw them and you want it to be challenging and so do they then it's not a problem.
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I dont fool myself into thinking that D&D is a work of fiction. I like that there's no guarantee for the heroes. No plot immunity. I like that if the heroes have fought and survived they've done so not because there's some greater story arc they have to finish but that they've legitimately done everything they could to survive against odds that would have killed any other person (any may have done exactly that) and have in fact SURVIVED.
As a GM? That is where I derive the most of my joy from. The player characters surviving.
This is a pretty clear statement of a D&D playstyle.
Other people sometimes play with other playstyles. For them, it can be
pointless to start a new PC.
In my current campaign, there have been three PC deaths. One one occasion a single PC died. I asked the player whether or not he wanted to keep playing the PC (who was level 2 at the time). He said yes - so together we devised a reason why the god of death would sent this person back into the world. That reason has gone on to be one major element of the campaign, although neither I nor the player knew that this would be so at the time.
On another occasion the PCs suffered a "TPK" - not really a "K", though, except for one who was dropped below negative bloodied hit points. For the others, they were just below zero hp, and in 4e that can be either dead or unconscious. I again consulted with the players as to what they wanted to do. All but one wanted to keep playing the same PC - so the next session began with 3 PCs regaining consciousness in a prison cell, which they were sharing with a stranger (the new PC), and able to smell the smell of roasting half elf (as the goblins helped themselves to the PC whose player didn't want to keep playing him). Meanwhile, the dead paladin was laid out on a ritual slab somewhere else in the goblin warrens, but soon dramatically returned to life as the ritual that the goblin shaman was using to someone the spirit of the dead paladin's nemesis also brought the spirit of the paladin back into his body.
This has nothing to do with "pantywaists" or "player entitlement". It's about what different players are trying to get out of the game. Not everyone is playing it for the same reason that you seem to be. (If they were, there wouldn't be any need for a unity edition.)
Personally, I also don't feel the attraction of placing a rust monster, and then making sure that the PCs find new treasure to replace what they lost. I just don't think that would add anything to my game. Why not just let the players keep the items they've got (which, in my game, are - at the ingame level - frequently gifted by patrons or the gods - and are - at the metagame level - based on player "wishlists").
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Not to mention the Inevitable Zombie Apocalypse... but that request was from someone who wanted to use the scenario later. That is the one where I got to use 300 zombie miniatures in a single encounter.... 
