Collecting useful things, like food and bedding material, is something that many animals practice and is a normal, largely innate behavior. We are all familiar with squirrels gathering nuts for the winter and birds carrying nesting materials back to the roost in spring. In addition, dogs burying bones in the backyard for future consumption is such a cliché that it's a stereotype of the species. Even we humans are described as hunter-gatherers in terms of our behavioral roots. But what of cats? Do they instinctively gather and store things? The answer is partly yes and partly no.
Not even scientists can’t seem to come to the conclusion of why cats collect random things like bottle caps, lipsticks, or toys. Some of them believe that cats think that these things are like their preys, while some believe that they consider these things to be like their kittens and gather them in the same way they would gather their kittens!