I am of those annoying, picky adults.
As a child I had a very severe bout of gastroenteritis. I lost so much weight, but as a result of the constant vomiting, refused to eat anything even after I recovered. I was then force fed, which compounded the problem.
After that I was simply petrified of food that was wet, or anything with a strong flavour. I would only eat bread, plain chicken, plain pasta, crisps and some fruit.
I made some headway very slowly, but any new food, and trying new food in front of people, was terrifying. Luckily my mum was understanding, but I vividly remember my grandad getting frustrated at a family dinner. I was say 8, and would not eat mashed potato. He came behind me, pinched my nose and shoved the spoon in my mouth. I proceeded to vomit all over the table.
I'm slowly recovering, and was only able to try new foods when I moved out and could try it without people pressuring me or watching me eat. I even ate some korma curry the other week. And wrinkles! A huge step! Even now though, if there is a particular texture, (such as the middle of a cucumber or tomato) I gag. It's very embarrassing and I don't want to. Thankfully, I have lovely friends who do not make a big deal out of it, and don't even mention it if I want to make some requests when we're out to eat.
Lots of people have very genuine issues with food. I have been reduced to tears when out with work colleagues who did nothing but make fun of what I ate the entire meal. I can see lots of people who'd do the same thing on here. It's a shame more people don't have a little sympathy and understanding.