I say this because everybody complains the first days are really hard on their bodies and nerves. So a smooth transition would make it easier to stick to the plan and reduce drop rates.
There isn't one group on the planet that wouldn't benefit from at least a little bit of Soylent at some point in their regular lives.
It doesn't have to replace their family meals, and it doesn't have to replace their social eating.
But it can be their occasional breakfast when they got up a little too late. Or their lunch when they need to run to the post office in their lunch break. Or their "eating at my computer" food when they're busy programming and don't want to order pizza delivery. Or their everyday staple when they're on a budget. Or their emergency food when they've just been hit by a tsunami and the rescue team won't come for days. Or their backpack food when they're on a military mission. Or their one-meal a day when they're in a submarine with tight space issues. Etc. etc. etc.
Example phase in:
1 soylent + 2 normal meals for the first week
2 soylent + 1 normal meals for the second week
3 soylent meals from then on.