Why did knights carry spices?

When the crusaders were exposed to different kinds of spices during the holy wars, they brought them back to Europe. Europeans were used to home grown plain food but with the introduction to spices, it completely changed their diet and left them yearning for more. Spices were expensive and they became a sign of wealth and the need for more spices arose which led to people like Columbus discovering America in search for a shorter route to the Indies in search of spices.