If you understand the term sandbox it’s basically refers to being single player or being in an open world (or room for this game).
I think this would be very useful for being able to test or try things such as curves, colors, powerups or maybe even practicing your skills.
For example, lets say you wanted to try out the Ghost curve because you see people absolutely dominating with it and wanted to know what it feels like before you bought it. You can try it out once or twice and if you like it you spend your coins on it and vice versa.
It’s kind of like a next level preview if you get me.
i have severe depression lol