I think you're overlooking a very simple reason why players might want PC death taken off the table: they like playing their current PC's. The campaign is more enjoyable experienced through and with them.I think group decisions like "PCs won't die unless the player approves" are simply ways of mitigating uncertainty on the part of the DM and/or players, strictly for the purpose of ensuring that random outcomes don't disrupt some overall goal or "story". While I don't like that style of play and tend to see "tory" as an outcome, rather than an intent, of D&D play...
It doesn't imply that there's a predetermined story or any grand design. This describes my current campaign.