Why does the garbage collection mechanism not clean up memory on the program stack?

The stack is a region of memory where local variables and function calls are stored. It operates on the LIFO (last in, first out) principle. Memory on the stack is allocated and freed automatically when entering and exiting functions, without the need for additional management.

The garbage collector is responsible for cleaning up memory in the heap — an area where objects are dynamically created with an indefinite lifespan. Memory on the stack does not require garbage collection because its management is strictly structured and predictable: when a function finishes, all memory allocated for its local variables is automatically freed.

Thus, the garbage collector does not handle the stack, as it is inefficient and unnecessary.