Of course you should have it for all of the obvious reasons: Wiping your child's snotty nose, to have on hand when (not if) you catch your child's cold, to put ABC gum into when your child hands it to you, to clean up the messy face of the same precious child after she has eaten a lollipop at the grocery store and to (again) wipe your child's snotty nose.
However, there are other, less obvious, reasons to carry Kleenex with you at all times.
Let's say your husband is planning on being gone for all of Valentine's Day evening because he is the director of the University Jazz Band, which always plays for the big formal dance on campus. Let's say you are feeling rather down in the dumps, because you will not be doing anything with your sweetheart on Valentine's Day for the second year in a row because of the above mentioned Jazz Band engagement.
After you have moped around a bit, you start to make dinner for yourself and the kids, and just when you have put your first bite of pancake into your mouth (yes, you made breakfast for dinner), the phone rings and it's your husband. He tells you that you have 20 minutes to get dressed up and he'd be there to get you. He indeed shows up soon after with one of your favorite babysitters in tow and you head off to the dance.
You get to eat the sit down dinner with him, and then you watch everyone dance while the Jazz Band plays. (Don't worry, being married to a conductor you are pretty used to sitting through things like this by yourself.) You say hello to a few people that you know, but spend most of the time just enjoying the music and people watching.
Sometime during the dancing you notice a young couple sitting at the table next to you. The girl is bawling, and her date is trying desperately to console her, but she isn't having any of it. Mascara is running down her face, she is searching in her purse for something (you assume for a tissue), but comes up empty handed. At that moment her boyfriend gets up from the table and asks the waiter for something, and is handed a totally unsoft linen napkin from dinner. You finally decide to just walk over there and hand her the package of Kleenex that is in your purse. That's all. No need for words, you're sure she's already embarrassed enough for having such an emotional display at what is supposed to be a romantic dinner dance. She uses several of the Kleenex and then her date returns the rest of the pack to you, incredibly grateful.
Soon after, they finally get up and start dancing. Then the music ends, you go and help your husband put music stands away and take down equipment and gather up music. Then you sit and people watch some more while you wait for them to load up their truck. You walk over to the music building with your date and make sure all percussion is put away properly, lock the doors and go back to the car and head home.
It might not have been the greatest way to spend Valentine's Day, but you did get to spend it with your husband and it was certainly much better than sitting around at home feeling sorry for yourself.
And anyway, aren't you glad you were there? Even if only to help some poor, distraught girl with your ever present package of Kleenex.