I am actually drinking a protein drink right now. I have one about once week because I don't eat a lot of animal products and I'm trying to put on muscle mass.
As for hair growth, I think if you are deficient in protein and then it will help grow hair, but be forewarned about that. Protein deficiencies are only common in "3rd world" countries because of starvation. It is said that most Americans consume too much protein. One of the symptoms of a protein deficiency can be hair loss, so I think this is where people get this from. But I think it only helps hair growth in people who were previously starving, such as those without access to food or recovering from an eating disorder.
And I really think it's dangerous for some of these ladies trying to grow hair to be consuming so much protein. Too much protein can be harmful, and I really think that if you eat animal products or lots of broccoli and nuts and don't work out heavily then you probably don't need supplements.
If anything, I think there should be a focus on things Western diets are usually deficient in, like certain vitamins. I hope you found this helpful.
I also don't think it's a good idea to be overdosing on biotin for this reason. Your body just doesn't use excess of most things.
These sources explain it better than me:
This is why you need it after a workout: Protein After Workout: Men's Health.com
This is the rarity of protein deficiencies: How Common Is Protein Deficiency? | LIVESTRONG.COM
What can happen with too much protein: 8 Side Effects of Too Much Protein. | Davey Wavey Fitness