Research, for the fun of it?

I love researching for the sake of it, to dwell on and absorb knowledge, but whenever a writer wants to apply research, one should know what it’s useful for before starting. Is it for a book? Is it to learn something to pass onto your readers? Pretty obvious stuff really. The trick is knowing why? Maybe research for fun, full stop, no more than that. Become not a know-it-all, but useful in some regard that you never thought about before. Research for fun may come in handy somehow.