Sandbox Mode gives you a second world on which to play the game as though it were not a game, but a toy! Earnings and prices no longer exist and you can build as many pieces as you like, creating the biggest and weirdest marble slides possible. If you want to, you can always turn Sandbox Mode off in order to go back to the idle-incremental world, which will exist exactly as you left it.
Sandbox Mode is especially useful for players who want to use the Twitch integration to its maximum potential. Being able to keep one world of play for streaming while having another world of play for your idle-incremental style is incredibly useful.
