Hi there!
(So they can blast things up for fun! Just kidding lol)
The history of the tank began in World War I, when armoured all-terrain fighting vehicles were first deployed as a response to the problems of trench warfare, ushering in a new era of mechanized warfare. Though initially crude and unreliable, tanks eventually became a mainstay of ground armies.
Hope this helps
-WolfieWolfFromSketch