There is no substitute for real food. I don't think anyone will argue that. (Except for maybe a supplement company)
With that said, meal replacements and protein shakes do have their place. They can be useful to those who have busy schedules. They're great for post-workout. I find them useful for cranking up the protein intake. I eat over 300g per day but could not do this with real food alone.
During the work week, I alternate solid food with protein shake "meals" (3 shakes per day). On the weekend, I only have one post-workout.