Why Can't `Box` Be Abstracted Away From the Developer?

Probably a newbie question, but the title pretty much says it all. I'm trying to understand the value of needing to explicitly put something in Box to store it on the heap, enabling things like recursive data types. Would it be possible for this to be implicitly done by the compiler under the hood when deemed necessary? I'm sure there is a good reason this isn't done, just trying to find the missing puzzle piece, TIA!