The people I know with restricted diets either have a medical problem or have issues around food.
Those with issues around food do get up my nose, but I am aware that most of them had these issues form very early on, with no help in getting past the problem into a healthier diet.
My mum has serious issues. Basically only eats meat and potatoes, rarely rice/pasta, and as little fruit/veg as she can.
And no skins on potatoes at all, so in the past when we've gone out to a restaurant she was carefully scraping the skins off boiled potatoes, complaining all the while. And yes, so, so picky at choosing meals when out.
The problem with having someone like this as a parent, is that the child picks up on these food issues and assume that's normal. When I met DP (nearly 27 years ago, now) I had a restricted diet, and gradually added foods I tried with DP.
Now I am almost 45, and it's really only in the last 5 years that I have made the connection between my diet and mum's. I sort of had to give myself permission to try all these wonderful foods out there, and I now have a wider range of food I like than DP
I had to realise that just because mum didn't like the food, it didn't mean that I couldn't. My DCs eat a lovely range of food.
I am overweight, but with my new knowledge about my diet and the issues mum has, I'm slowly starting to lose it simply by eating less (and better) and moving more.