From Battle for Zendikar to Ixalan, every block has had at least some nod to white/black draining life (Dominaria has repeatable life loss, but no W/B drain card)
Roxanne, Starfall Savant is the type of card that can ramp into an 8-drop with ease, benefits from the Treasure the turtle leaves behind, and even makes good use of the damage redirection since Roxanne's a frail 4/3 that needs to be attacking to function
Long story short, there are tons of neat ideas and reasons why you might want to make your own cards
Now there may be times when the grabbing of lands is prohibitive, and winds up handing the game to your foe as they blow you out with a giant Secure the Wastes or cycled Decree of Justice that makes 17 dorks off the 9 new lands you gave them as they ran a deck that went wide with tokens
I know other builds will run these, I just did not think they fit this particular build