There is nothing stopping you from eating food for enjoyment. Soylent replaces food for fuel. If I were to live on Soylent, I'd still go to restaurants with family and friends, and they'd probably be more enjoyable as I'd be used to the taste of Soylent.
Maybe, but then why do people using Soylent seem to be making a full switch and only eating that full time instead of mixing food intakes? Every blog post about Soylent is about people who stopped eating real food for good for x weeks.
They probably want to know what it's like to live on Soylent for an extended period of time. I did see a video by Motherboard/Vice where he drank it at a restaurant which I think misses the main point of Soylent.
Eating the same food every day for a month will make you crave different foods, even if it's Soylent.