As with other supplements that are out in the market, it's always best to consult with your primary doctor or nutritionist before making the final call to include this in your daily eating habits. In my opinion, nothing beats getting your daily value of protein through lean protein options and nuts. But in a high speed, busy world, we're constantly on the move, and unfortunately many of us "don't have time" to cook or prepare meals.
This is where supplements (and for the sake of this article, protein bars) have a particular role. For the most part, protein bars provide the body with a dose of high quality, nutrient-rich blend of protein, and in some cases, essential vitamins & nutrients that (many will argue) you might not find in cuts of meat, fish, even nuts.
The good news is there's various types of protein bars that may be suitable to your needs: whey, whey protein isolate, and soy (to name a few). Some can go as low as 10g to about 30+ grams of protein per bar. How it will be beneficial to you will depend on your goals and how the additional calories from carbs and fats will impact you and those goals. It's also important to note that it shouldn't be the ONLY source of food to partake throughout the day.
Nothing beats solid food. Eating a variation of complete proteins that are derived from milk, animal & nuts are more beneficial to you than protein bars. What I typically recommend my clients is this; if you're on the run, and in need of protein & you don't have other solid food choices, then it's fine to consume either a protein bar or shake. Most importantly, it SHOULD NOT be your only choice of protein at your disposal. So I'd recommend to meal prep or have a couple servings of nuts at your person from time to time.
Because of it's convenience, snack options, and from time-to-time meal replacement ideas, there's no question protein bars are here to stay. While it may provide some benefits that you won't receive from other Protein sources, it's ideal to educate yourself, and if it's a decision to implement, see how it fits best in your diet.