Bartering is as old as Civilization itself. When you need a product or service, someone always comes to provide and fill your needs. Bartering is actually at the heart of all ecomonic markets. In the event of a catastrophic event money will hold no value. And you can only stockpile so much.
Disaster may strike and the worst possible scenarios become reality. Items such as food, and weapons are what remain valuable during dark times. It's certainly a goal to be prepared for those SHTF situations. But more likely than not, a sceario you are not prepared for is going to hit. Just by storing some universal items you can make up for deficiencies which would otherwise put you in a much more dangerous situation. Simply by trading, you can increas your chances of staying alive longer.
Trading one item for another is just one aspect of bartering. You can also pay for goods and services in return for a favor, food, or shelter. There may come a time when you need something someone else is equipped to offer. .