I take one knife with me (victorinox on the keys doesn't really count), but I am a city person and it doesn't really make sense to carry more than one knife at a time.
I understand people carrying their favorite $2000 custom and a cheaper $20 kershaw so that people can borrow their cheap knife.
I have nothing against carrying multiple knives, in fact if I were to go camping I'd easily pack more than two blades...
The practicality of having multiple blades really depends on where you are and what you are doing. If you job requires it or you are out in the wilderness, sure. But if you have an office job, and you day consists of commute, office job, commute, I really don't see a reason to have more than one knife on you at a time...