Magic: The Gathering was designed for the downtime at gaming conventions.
In 1991 Richard Garfield, a math PhD student, was asked by publisher Peter Adkison to design a portable game playable in the downtime at gaming conventions. Garfield’s insight was that cards wouldn’t be equal — you bought them in random packs, and rarity made a scrap of cardboard worth money.
Magic: The Gathering on Brandseum