By having friends who have ridiculous amounts of leaves already handily raked into a ginormous pile two things are universally true:
a. Playing at a friend's house is always more fun than playing at home, i.e. playing in their leaves would be much more fun than your own lame leaves.
b. If leaf playing is done elsewhere, this allows the mother to not have to rake her own leaves for the entertainment of her children. Or even worse, to have to re-rake the entire yard after her children have decimated the leaf pile. -shudder-