Everything in their house gets replaced so often that the kids probably haven't been taught to look after their toys and belongings. Where are they going to put soft play toys?? If it were for outside they would still have to find somewhere to put them inside.
Probably have weekly spring cleans and are on first name basis with the skip company, why don't they only buy what they actually need, the amount of clearing out they do would suggest they buy anything and everything just for the sake of it. How many prams has millie had for example, ophelia is only 7 months and has had at least 4 prams already, there are more productive things she could be doing other than clothes shopping.