They like the novelty. The same thing in a new context becomes a new thing, new things can potentially be good/useful/tasty and must be investigated and tried. Humans do this all the time - taking a familiar thing and doing it in a new way, in a new place, etc. and suddenly it's more enjoyable. Drink your coffee in a fancy new mug. Read a book in a rocking chair instead of on your couch. Schools do it - hold the lesson outside on a sunny day, sitting in a circle on the grass, instead of at your desks. It's still the same coffee, the same book, the same lesson, but when presented in a new way, suddenly it's more interesting. Animal brains (including ours) are drawn to novelty because of the potential for benefit in it, especially when it's clear that there's no danger (because novelty has the potential for danger, too).
