Some people play competitively and will buy only the cards they need off the second hand market.

Netdeckers do the same thing.

There are some communities that are all about deckbuilding and allow participants to just make proxies of anything they don’t have.

Typically in such games cards like Black Lotus are too far outside the power curve and are pre-disqualified. Most MtG tournaments only allow cards from the current basic set, the last major expansion and whatever minor expansions have been released since. And Black Lotus is no longer in print.

In fact, the lesser Lotus Petal was restricted then banned for being still outside the power curve.