I believe that it was clever marketing when google first did it when gmail was first released. I feel like the storage is only part of the service, it's access to your files everywhere that they are really trying to sell.

Knowing that most cars are bound to depreciate quickly wouldn't stop me from accepting a nice, new, free one.

not to mention you got 50g for referring a friend, or just registering a second account, so almost everyone already is at 50g