It’s fantastic for you that you have the time, knowledge, facilities and motivation to plan, prepare and eat three balanced meals a day. A lot of people are missing one of those four and I think that’s where the appeal may be. I probably wouldn’t replace one of my meals with something like this but I can totally understand why it’s appealing to people. That’s not even taking into account the cost for those who would otherwise be buying lunch on a work day. The powdered Huel is less than £1.50 a meal - you can’t even get a coffee in London for that.
(You both have very different recollections of military rations to me. We called them ‘Rat Packs’ for a reason… )