Answer:
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it, can't see it. What is it?
I only exist when you are here. Where you never were I can never be.
Soft, hairy, from door to door. I am the pet that always stays on the floor. What am I?
The last man on Earth received a phone call, who was the caller?
When it comes to me, you go on red and stops on green. What am I?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.