Seriously. I do this all the time. You probably do it too. You see some book in a store about some kind of questionable content that you're curious about but wouldn't want people to know you're curious about it because they'd give you funny/worried/disgusted looks and question you're sanity/morality. But you get it anyway, firmly telling yourself it's research for your book.
Or maybe you decide to take karate lessons, not because you're just interested but because that side character in your book that shows up for one scene does some pretty awesome kicks and stuff and you need to know how to describe such things! So you have to take lessons!
Or you know that place in New Zealand where you're book takes place? How are you ever going to describe such scenery without having been there first!?
And that stuff you read on the internet in the name of research for your book. . . Goodness help you and the poor soul who decides to look at you browsing history. They'd be sure to send you to a mental hospital despite your pleas of, "It was for my book!"
And it is for your book, really. A little. But not wholly. Lots of times it's purely excuse, others it's only part that. Like my reading up on witchcraft and alchemy. I had found myself wanting to glance around at those two subject in the bookstore but never did. Until I found the perfect excuse. You see, having trouble coming up with a magic system I saw that section of books in the book store and it hit me: witchcraft. Alchemy. Those might help me with my magic system problems!
See? The perfect excuse. I really am reading them for that purpose, but not wholly, some of me is just genuinely curious about it, and I'm using writing as the excuse to not get those funny looks.
But hey, it works.
So what have you used writing as an excuse for? Vacations? Musical instruments? Some really really old and expensive book so you know what paper and book binding was like back in the day because of that scene where you have to explain that?