I understand why people get Soylent, but I'm also wondering why people choose to trust a company to provide the powder for them instead of making it themselves.

Not only would that save you quite a bit of money (Soylent is a pretty poor value proposition if you need to consume more than 2000 calories), but you would then personally control the freshness of the ingredients.

There are so many recipes at diy.soylent.com/recipes and many of them are made from ingredients that combat the main problem of buying food at the supermarket - spoilage and waste, by letting you pre-mix months worth of food that doesn't go bad. And with the money saved compared to actual Soylent you can supplement with whatever fresh foods from time to time.

It's not like the nutritional profile of Soylent is hard to achieve - all you have to do is solve a system of equations for the necessary macros and vitamins.