you don’t have to think for yourself what you want, or make your own choices as the set menu of what’s in the deal is presented to you, with a limited selection of what’s in the offer.
I'm autistic. I'm in the middle of my work day. I am not in a position to be thinking hard about food at that point. I don't have access to a kitchen at work to start assembling food in. If I'm lucky, today's site has a fridge to put a from-home lunch in, but I don't know that until I get there if I've not been to that site before. If I'm super-lucky, there's a microwave, but I'll be queuing for that.
Tesco usually have a GF meal deal, either a sandwich or some sushi (please, Tesco, never stop doing GF sushi because no one else does it). I don't have to worry about it getting warm and giving me food poisoning if there's no fridge because I buy it immediately before I eat it. I don't have to heat it. I can carry it to somewhere quiet and get away from the break room without being told "no hot food outside the break room, it's a hot spill hazard" or "not hot food at your desk, it stinks the office up". I don't have to find somewhere to prepare it. It won't leak into my laptop and keyboard and mouse on my journey to and from and between sites.
I think that you and others on this thread don't understand the challenges of having a job where "going to work" means going to a different place every day, especially on top of being autistic.