Protein bars or shakes offer no benefit, its the same as protein from food, they are just convinient sometimes when ur out or on the road or whatever in order to meet ur daily protein needs.
Convenience, which you mentioned, is a benefit. Cost is a benefit also.
I would even argue that it's not the same as protein from food in general. When it comes to muscle building, proteins are not all the same. They are different in digestibility, rate of absorption, and amino acid profile. Whey protein is the fastest digesting protein, so if you drink it after a workout it will start to benefit you quicker while your body is in its most favorable state. More importantly is its amino acid profile. Muscle protein synthesis (the building of muscle) is triggered by the amino acid, Leucine. Other BCAA's like Isoleucine and Valine are important too so you have a balance of BCAA's. Whey is the protein source with the highest concentration of Leucine and also has large amounts of Isoleucine and Valine, so from a scientific perspective it does provide additional benefits over other types of protein. From an anecdotal perspective, I've been keeping track of my caloric intake with MyFitnessPal on my phone, and I've switched between whey and plant-based protein. I noticed that when I stayed on the same diet but switched from whey to plant protein, I lost weight, but not in a good way. I could feel myself losing muscle mass and not being as strong in the gym. I went back and forth and tried it again, and the same thing always happened. I actually wanted to be on plant protein for other health benefits, but not at the cost of lean muscle mass. From my perspective, the effects are real.