There are plenty of reasons. It strengthens your bones and muscles. It is gentle exercise for your ankle, knee and hip joints. Hiking can reduce your sugar cravings and you burn off calories. Hiking reduces the risk of lifestyle-related conditions like diabetes and cardiovascular diseases. It may also increase your ability to relax and reduce feelings like nervousness and stress. It can improve your memory and prevent dementia. Besides, it is the cheapest and most simple way of training.
Find some good advice prior to the hike.