@Meanlucario
It’s to make each one worth something and meet with others to trade what you can’t get on yours. To be social with others. If that’s your criteria, then trading card games are “bad practice” since you don’t have every card in the pack you get.
Honestly, I think the inclusion of the internet kind of ruined trading, because they took that face-to-face out of the equation and became very robotic.
I think that’s why Pokémon Go became so popular since it kind of brought back that comradery, although dumbing a lot down in the process.