Making characters is just a fun thing to do, if there's enough to it.
It can also inform part of the character backstory too.
For example, I built a Pathfinder half-orc barbarian with alternate racial feature called 'sacred tattoo' that grants a permanent +1 luck bonus to all saving throws, then picked up a trait called 'fate's favored' that adds an extra +1 on any luck bonus, doubling the saving throw bonus I'd obtained. Another racial trait, 'shaman's apprentice,' granted me the Endurance feat.
So, using this backstory, I decided that my character was a child of a reclusive orc shaman and his human slave wife, raised in cruel conditions and branded by his dark magic until she could stand the abuse no more, flying into a rage and killing her father, then abandoning her home and wandering the world as an adventurer in search of a new life and family among her companions.
The mechanical benefits often come with flavor text that can help inspire more of a character background than 'hatched from a murderhobo-egg.'