Protein powder isn't necessary if you're getting enough protein in your diet through food, but that's why it's considered a supplement. No supplement is necessary.
I have definitely had good results with different things I've tried. A lot of it just depends on your goals and what kind of exercise you're doing.
I drink a protein shake during the day because it's too hard for me to get the desired amount of protein through my regular diet.
The biggest problem people have with supplements is using them the wrong way. Certain supplements are designed to do different things. I only ever try something once I've done a good amount of research on it. If you drink a protein shake after a workout without knowing why you're doing it, chances are you're also not paying much attention to the rest of your diet either.