The combination of maximum (or even above-average) HP at 1st level with provision for being "out, but not dead" at negative points can nearly eliminate PC deaths short of coups de grace. I have found the latter provision particularly odious, though; I would rather employ some sort of saving throw if I want to make such an allowance.
Without such modifications, 1st-level characters are indeed prone to high mortality rates -- very high in combination with novice players. Of course, lack of skill can doom characters of any level!
I think the low-level game is key to initial development of essential skills, and excellent for getting back up to speed when those have gone rusty. It can also be a great change of pace after a lot of high-level play, offering distinct challenges.
Once upon a time, it was also commonly a process of real discovery by players who did not know thing one about the monsters and magic of D&D. (For that reason, it was preferable if at all possible to play for a while before "parting the veil" by reading the material a DM needed to know.) The death of a character was (for most of us, in my experience) not a big "bummer" but an addition to the thrill -- and an opportunity to roll up another, perhaps of different sort. The toss of the dice was delightful suspense, and the dungeons always held fresh mysteries in their depths. I would give the analogy of a friend's cat that fell out a window, survived without serious injury a bounce off a (parked) car ... and, as soon as it was retrieved, seemed intent on jumping the same course! Whee!
When one has "been there, done that" times enough to get jaded, one may wish to skip that phase and start at (say) 4th or 5th level. I prefer that to "jacking up" 1st-level PCs. However, I also prefer to hand-wave the competence of such characters as primarily the result of being especially gifted -- as opposed to coming up with "back stories" as copious as the tales that actual play up to that point would have produced. The biography that really matters, in my view, is what emerges in play.