It's amazing the stuff you have to look up for stories sometimes. Last week I was deep in the rather arcane regulations surrounding the use of child car seats in the UK. Yesterday I had to research the lead actor's name in Twilight (Robert Pattinson, in case you didn't know either) and Russell Crowe's age.
None of these was for the major theme of a story, but just those off-the-cuff little remarks that can make all the difference if you get them wrong. I've seen this myself when I've had my reader hat on. Years ago I found a story in which the hero was on a cruise ship which docked overnight in Paris. A Paris that had miraculously translocated itself to the French coast. By the time I'd finished boggling, I'd totally lost track of where I was in the story and had to go back and start it again. I'd hate that to happen to anyone reading my work.
Besides, it's actually a lot of fun. You never know what you're going to have to find out about next.