I see the following happen at least once a week. Two toddlers are playing in a room filled with toys. One child grabs a car, and what a coincidence, the other child wanted to play with the exact same toy. A fight ensues.
The scene always reminds me that scarcity is a driver of value. We appreciate things that are in short supply more. This makes it an interesting concept to use for marketing purposes.
Limited availability makes a product more exclusive, which can entice people to pay a higher price. Scarcity also speeds up the decision process, you do not want to miss out one the limited edition of whatever it is you are interested in. Finally, if people own something few others do, they like to talk about it. And word of mouth is the best advertising there is.