In this day and age may not make sense to still keep a tire pressure gauge. Any decent gasoline station already has one built into the air pump. A good gas station will have one that is properly calibrated. However, keeping a quality gauge handy is better than not having one at all. Here are the reasons why:
You might find yourself in the far-flung province one day, and you are at the side after getting your tire repaired. An overinflated tire can be pretty dangerous, and there’s really no surefire way to tell. Sure, you can touch it, but even that method cannot be as accurate as having an actual gauge.
My gauge is made in Japan, and it brings be back to the time that my Dad would bring me along with him for car maintenance and repair. He had his own gauge, and I really wanted one of my own. These pen-style gauges made of metal are getting harder to find now. If you come across one, buy it. I found mine in an old auto supply shop in Baguio.
Or my job, rather. If something feels off with the test car that I am driving, I bust out my gauge. More often than not, the tires are overinflated. This is done by the manufacturer to compensate for air loss that happens during shipping. If the car is brand-spanking-new, the tires probably haven’t been aired down from the trip.
If you do any track days, a tire gauge is an essential tool. The right pressure can spell the difference between a good lap time, or a bad one. A tire thermometer is also a good tool to have, to determine whether or not your driving (or the car’s setup) is ideal. But that’s for a different story.
Before taking off on a road trip, knowing your tire pressure is one less thing to stress about. You don’t want to be traveling without knowing if your tires are holding the right pressure. It’s great for fuel economy, and above all, safety. Check the owner's manual for the recommended pressures for your car. The pen gauge is tiny, anyway. Better to have one and not need one, than need one and not have one.