While it's more apparent in history-heavy historical romances, readers glean all sorts of knowledge from romance novels.
For example, reading sports-heavy authors such as Jaci Burton, Susan Elizabeth Phillips, and Rachel Gibson will give insight into athletes and athletics. Perhaps you didn't know anything about gambling before reading Sarah MacLean or Cecilia Grant, or botany before you read Adele Ashworth. Maybe you picked up a few cooking tips from Louisa Edwards, or knitting skills from Debbie Macomber.
What's the neatest thing you've learned about from reading a romance novel?