And they’re usable in that capacity, too!
Grant Thompson, the “King of Random” at Instructables, explains how to make them. You can buy a pre-made silicone LEGO brick mold or make your own. Thompson prefers the latter option and describes how to do that. It takes precise work to produce bricks as clear and well-formed as these, but the results are worth it.
Hopefully he can scale this process up to large Duplo blocks. We could build enormous gummy structures with sufficiently large bricks.