I suspect the reason this is so difficult is also the reason that I would pay a lot for it: it's a huge pain to come up with many recipes when you're allergic to many things. I'm allergic to almost all legumes. That includes soy, peanuts, lentils, edamame, most beans, peas, licorice, etc. However, I'm not allergic to black beans. This combination of allergies is highly unique: I'm sure there aren't that many people out there who share the exact same allergies. Sure, maybe some people have overlap, but it's likely only a partial overlap.
This means that any meal kit service would either have to 1) Provide bespoke sets of kits for almost every allergy combination possible or 2) Provide a limited number of meal sets that hit the big categories. Option 1 is nigh impossible since that's too many combinations to gain the benefits of economies of scale. Option 2 also sucks because my allergies might get lumped into a broader category and I miss out on ingredients. (Eg. I actually can eat black beans, but since they're legumes, they would likely be banned from a 'no legumes' set of meals)
The closest service I've found is https://paleoonthego.com/collections/aip-bakery
However, I think they fall prey to my option 2's issues. No nightshades??? What the heck? I love tomatoes! Additionally, I haven't even bothered ordering anything from there because the items are so expensive. Just look at some of the prices: $22 for 4 pop tarts! So in fact, not only did they fall prey to option 2's issues, but they also fall prey to option 1's issues! (lack of economies of scale)
I have no idea if this issue is ever solvable in a way that provides a stable business model. Frankly, if normal meal kit services can't make it work, I doubt one that artificially limits its customer base would work either.