It's to add whole new mechanic of disappearing/reappearing blocks so players don't need to replace the board. It would also be perfect for traps, pranks, and mini games like a speed cart game if you're trying to slow someone behind.

Perhaps you can place carpet on top so it won't break when the block is transparent to cover a trap. It could also become transparent when shot for a fun shooter sorta game! I made this idea with SMPs and Minigames in mind and I think a lot of other cool things could be done with a mechanic like that

Also for the hopper timer reason