I've been to Thailand. One time I was in a restaurant that catered to tourists, and two of the tourists at a table near me told the waiter they wanted the food to be really spicy, because they weren't like those other tourists who couldn't handle the heat. They told the waiter to prepare it like it was for Thai people.

So, the food arrived and they thought it was a joke. They couldn't manage to down a spoonful of it. So, they called the waiter back and tried to call him on the bullshit by having him try it. The waiter tried it, said "yep, tastes good" or something, and asked if they needed anything else. They sheepishly said no, and he left. I think they just left their food uneaten and left.

Point being, if you really eat spicy food all the time, you develop a certain tolerance. What might seem like incredibly spicy food for someone (even someone who likes spicy food) might seem like nothing to someone else. If you're used to something crazy hot, you need all that capsaicin just to make the dish interesting.