There are a variety of other reasons why people might want a stronger grip in their hands (eg. people who are into rock climbing), but their goals will be roughly the same - to build the muscles in their hand so they can strongly and firmly hold something in place. For bodybuilders having a good strong grip is also handy when lifting the heavier weights.
Some people also build stronger forearm muscles, which also effects grip, so absolutely that is another reason to be doing grip exercises.
There are essentially two ways to do this...
#1. Sports Hand Grips and Weightlifting Grips
You've probably seen them in stores before. Its basically just a device with a spring that you squeeze together. Its not complicated or expensive to purchase them, and they do "most" of the job they are advertised to do.
When buying grips you will want to start with a low number - like 30 lbs or 40 lbs. You can even get adjustable grips where you can change the tension in the spring.
The more heavy duty weightlifting grips start at 100 lbs and go up to 300 lbs, but that is more for serious weightlifters.
#2. Old School Frugal Grip Exercises
These are arguably the better way to attain a stronger grip. Why? It gives you more range and variety, offering you more of a challenge and will push your muscles further than any mere gadget will do. The types of grip exercises will give you different things to challenge yourself with - and the beauty of these exercises is that are not only better for you physically, but they're easy on your wallet too.
Look at the visual examples below of various grip exercises you can try. You won't need anvils or weights to do some of these exercises. When lacking in equipment try using books and heavier objects in your home or garage. Rope climbing is an excellent method too as it uses your body weight instead of the weight of the object.