Why? First, you never know. Maybe they legitimately want your skillset - why fake up some crap you hate for a job you don't need? Second, you'll get practice taking interviews in a very low pressure situation. Worst-case they laugh at you and you fly home. Best-case you get an unexpected job offer you can evaluate. Either way you got some practice and "game time" with the process so if you're ever in a more high pressure situation (e.g. you really need the job) it's a lot easier.
Plus, smart people meeting other smart people is never a bad thing.