Mostly, I'm tossing ideas out there. I'm tired of Con being everyone's second or third choice. It's boring. It's a non-choice. There are other ways to solve it (I'm a huge fan of 4E's Con mod to healing surges).
What are your thoughts on Con?
First of all, I agree that almost never a PC has a low Constitution score. It doesn't matter how many people chime up in this thread and say "I once played a low-Con PC and it was fine". I actually believe is IS fine, but I don't believe that players do that more than very rarely anyway. The vast majority of players are simply too scared by having their PC killed, they know that high Con means more HP means less likely to die.
That said, I am very disappointed to read in this thread suggestions that take away from Constitution, as a way to discourage players from boosting it. This basically means "let's make Constitution suck, so nobody takes it!" This does not so much solve the problem, but creates a new one! Every PC will be weaker and more likely to die as a result. In the best case, it'll make players look for other ways to boost their HP.
Instead, try to offer bonus HP to everyone, so that taking even more from Constitution would be overkill.
The way I handle it however is very different, but it is grounded in a specific gaming style that most do not want, so I am suggesting this: essentially I tell my players that their PCs will truly die only if the players agree, otherwise a "technical death" will default to some other penalty (captured, stranded, unconscious, lingering wound, or even permanent loss). So my players know that they don't have to worry maximizing their chances of survival.