Why is tropical cuisine spicy?

I've mentioned this before, but it's worth repeating:

Spices from the tropics were always a luxury item to medieval Europeans, and now their descendants can afford more of them. Spicy plants are more common at lower latitudes because spices are commonly anti-parasite poisons evolved to protect the plant from the teeming variety of parasites found more in year-round warm climates than in wintry climates. (Also, biodiversity is greater in the tropics due to more specialization because of fewer seasonal swings). 

Thus, 15th Century Europe’s equivalent of the space race of the 20th Century was to find shipping routes to the Spice Islands of the East Indies to bring back peppers so that meat could be preserved longer against parasites.  

Thus, cuisines get blander the farther north you go (as shown by Garrison Keillor's jokes about Norwegian cooking), in part because there are so few spicy plants growing at latitudes where winter kills off most parasites. And it was easier to get snow and ice to keep your food refrigerated so you didn't need as many spices. (For example, a major product of 19th Century New England was ice. Riverboats plying the Mississippi might carry hundreds of pounds of ice from Walden Pond.)