Do you put at least two pens in your purse, backpack, or carry on bag?
When traveling somewhere other than the US, you'll need to fill out forms. Sometimes on the plane...sometimes standing in line...sometimes just one in your traveling family...sometimes everyone in your traveling family.
If you've remembered to put a couple of pens in your purse or carry on, good for you. If you've remembered the pens, but put them away or at the bottom of a bag...good luck finding them.
It makes life and traveling easier if you have them within reach.