Lifestyle? IIRC, the creator of Soylent had a busy lifestyle and as a result barely had time to cook or eat and that's why he created Soylent.
Some people prefer not to spend time on cooking.
There are many times where I just don't have time, desire or energy to cook a healthy meal. A healthy meal replacement is a lot better than ordering pizza.
Don't assume that a busy lifestyle means 'overwork' - I just have different priorities.