There's a lot of legacy in it. You usually want the last name separate when you want to be able to sort users alphabetically by their last name instead of thei

There's a lot of legacy in it. You usually want the last name separate when you want to be able to sort users alphabetically by their last name instead of their first name or nickname. But this admittedly makes less and less sense in the age of search and monster datasets. Also: for personalized content. "Hi John" is better than "Hi John Smith" when sending email. There's a gazillion ways to fail extracting the first name when a name doesn't follow a [first] [last] name format.