Kandyan Wars happened in 1796.
China.
Qin's wars of unification happened in -230.
Anglo Marri wars happened in 1880.
Long War - Ottoman wars - happened in 1591.
Probably, the most basic answer anyone can give, is because humans exist. While humans are alive, wars will happen.
Meteos Wars happened in 360.
Ozma Wars happened in 1978.
Mytran Wars happened in 2009.
X-Wars happened in 2002.
Gemini Wars happened in 2012.
Carnatic Wars happened in 1746.
Arena Wars happened in 2004.
Trade Wars happened in 1984.
Neon Wars happened in 2006.
Bomberman Wars happened in 1998.
Advance Wars happened in 2001.
Astro Wars happened in 1981.