Various reasons. Natural loss of taste buds usually starts much later in life, usually past the age of 50. Irritants, especially chemicals can damage taste buds. If you are losing your sense of taste, there are also other medical causes that need to be looked into. Consult a physician if concerned and want answers for your specific set of circumstances.
Never except diseas. Certain diseases can cause loss of taste buds, as can certain medications. With aging, taste buds can have decrease sensation.