I totally didn't just use this image because it was open-domain. Totally not!
3. Practical Everyday Use
Haven't we all had that loose string in our shirt or jacket, that threatened the entire livelihood of our garments? With the heart-pumping stress of sharply pulling down on the loose string, and possibly risking the rapid unraveling of your sweater at the start of your day, wouldn't it be better if you had a unspecified sharp apparatus that could effectively cut such a problem? Along with cutting loose strings, a handy pocket knife can easily help you open envelopes, cardboard boxes, and even hard-to-open plastic packaging.
Look at all those uneven wrinkles and creases! Won't anyone think of the children?!
Carrying such practical tool with you everyday will not only make your life easier, but help you satisfy your hubris of dominating everyone around you. In a theoretical situation that involves a hard-to-open cardboard box, your significant other, and your nemesis, who would impress your lady-friend, if you had a handy-dandy, heavy-duty knife on hand at all times? If you fail the peacock courting process, you could easily turn the tables by physically dominating your opponent in a knife-to-fist fight, it's a win-win.
Except for the jail part.
2. Self-Defense
While we're still talking about unnecessary violence, sometimes, you might not be the aggressor; you might find yourself being attacked one day on your daily stroll to your (as often as you go) local soup kitchen. Short of a full-fledged firearm, what better incentive would the criminal need, to run off and tell his gang that he couldn't rob you because of your beautifully threatening knife? Even if you don't walk down strange alleyways with gangs on every corner everyday, the confidence and security that that a knife provides might give you that extra boost to leave your house in the morning after pissing off your postman.
"If only I had a pocket knife! And opposable thumbs!"
But I know what you're thinking. "Isn't it impractical to fight someone with a 1-3 inch blade?" (In most places, a 3-4 inch blade is the longest blade you can own without a "special license") However, this isn't the case; if a person knew exactly where to stab, a one inch knife can easily subdue a full-grown man with the urge to kill. Cutting the right arteries at the right places can cause a person to bleed profusely to death within a few minutes if not seconds.
1. Keepsake
While giving your son/daughter a brand new iPhone or iPod would be great, there's a small dilemma: within almost a year's time, your gift would instantly become "out of date" and therefore "not cool" in the eyes of society. Replacing the Apple products with a car, TV, or any other tech gifts, you still end up with the same problem; anything you buy now will probably become a relic of the past within a decade or less.
However, unless they start making new innovative knives made out of pure light, a knife can become a timeless keepsake that's passed down from generation to generation. I mean, I doubt that you'll like a big-block phone from the 90s as a keepsake gift from your 'pop. (However innovative it was in the past.)
"I've got your graduation gift right here! I'm sure you'll love it just as much as I did." - Technically Impaired Parent
With each knife having its own type of "personality", you'll be passing down a extremely individual gift that might provide a more meaningful link to your children. The manner in which you use and sharpen the knife, would probably determine what the knife does best, how it performs, and the condition it'll be when its your time to it pass down. While a large gold grandfather clock would be useful good-looking, a knife is something that can be carried and used everyday until the day you clinically die.