They have different formats that people play with varying amounts of sets being legal, one of the most popular formats is a casual format where almost every card printed is legal. Sure a lot of it becomes chaff, but it is not unusual for cards you buy to appreciate in value, or even gain a substantial amount of value when they become viable and popularized in decks or are enabled by new cards that are released.

The cards I played with decades ago when I was a kid in school have appreciated in value many multiples of times over.