But sometimes you don't need the mana right away, and you'd rather get some sort of bonus from the land you grab
Lord of the Pit (Alpha Edition) $105,000 BGS Pristine 10 Why It's Valuable: One of the most feared monsters in early Magic
This ability does set the stats of the resurrected Pirate to 4/4, which may weaken some of the bigger targets, but for the most part, this is actually a positive, turning your aggressive early Pirates into legitimate threats later in the game
Pokmon is returning to McDonald's
There are also creature-lands like Lair of the Hydra that have an activated ability that animates them into creatures, and some planeswalkers, including Gideon-type walkers like Gideon, Ally of Zendikar and Kaito, Bane of Nightmares, that have activated abilities or triggered abilities that let them become creatures
I could not confidently tell you what is in the current version) but the downside is cognitive load