Why play? There are many reasons. This is mine.
Our ancestors are within us. For roughly 200,000 years Homo sapiens sapiens has roamed the planet, and it's easy to forget that we, as our even more remote relatives, are nomads by nature - hunter-gatherers, wanderers, vagrants. It has only been a puny 8,000 years since our style of life has become sedentary, since the concept of 'city' or even 'village' appeared, since both the blessing and curse of 'civilization' were realized. Man is - both physically and mentally - nomadic.
Vagrancy is in
our genes, a heritage from our nomadic ancestors.