I play on a roleplay server in World of Warcraft so it's at least practical to have a working knowledge of the lore around the characters you create.
For starters, It's useful to know that if you were say, making a Night Elf, they're likely thousands of years old, not 18-25
like I see a lot of people pretending to be.
Or if you're playing a Draenei, NO you were not born on Azeroth, you were born on a spaceship or a different planet.
And the amount of times I see human players talking down to dwarves and calling them 'boy'... No sir, it does not work that way!
The average middle-aged dwarf is 130 years old, No human has the right to call a Dwarf 'boy'.
I guess since that kind of got a bit ranty towards the end there (I'm serious about my dwarves) that maybe Lore is pretty important to me.