Haha Zokambaa, I think these restaurants tend to tone the food down because they want their customers to keep coming back.
The inability for restaurants to supply an adequate level of heat seems to be a common complaint for chile heads, and I've read from others in different countries with the same concerns.
There is an Indian restaurant in Edmonton called the Red Chili that we ate at recently.
I asked for a spicy dish and they gave me the hottest one on their menu and it was quite notable in it's high level of heat.
They also brought out some very hot spicy pickled peppers for use as a condiment.
I'd have to say that receiving that level of heat at a restaurant in Edmonton is rare and that's why I will carry a shaker of hot pepper powder along, whenever I can remember to bring it.
So I guess you'll have to take matters into your own hands Zokambaa and bring along a bottle of either the hot sauce or powder of your choice to season your food to the desired heat level for your liking.
dvg