Meal replacement shakes can be useful when you're trying to control your calories while still getting what you need. Particularly good when per iodising your training, so you might still need measured amounts of protein and carbs but you're trying to lose fat after building muscle. Very easy to measure out 1,500 calories worth of powder a day vs guessing calorific content of food.
Having said that, I don't get why the current geek love for Soylent when there's really no shortage of meal replacement shakes out there that seem to do the same job but cheaper. I also love actually eating food, so would only use a shake for a short term goal.
Because I would rather (a) make my own soylent or (b) buy some from an open-source distro like Rob's than (c) buy some from a cheesy corporation like whoever makes Ensure.
Having said that, I don't get why the current geek love for Soylent when there's really no shortage of meal replacement shakes out there that seem to do the same job but cheaper. I also love actually eating food, so would only use a shake for a short term goal.