Neither does most of the community. We call it proxying. Of course it's not allowed in sanctioned play because the purpose of sanctioned play is to sell cards, but I've never been around a table in someone's basement who cared that the sol ring I just played is actually a mountain with "sol ring" scribbled on it in sharpie as long as there was no way of telling it from the other cards in the deck, it would be legal for a real sol ring to be in that deck and I played it according to the rules governing sol ring. There are different formats to magic and the one with the most extensive, and therefore expensive, list of permissible cards has competitive decks that run into the tens of thousands of dollars invested (https://www.mtggoldfish.com/metagame/vintage#paper). If you had to buy all of that every time you felt like playtesting a new deck people simply wouldn't do it.