[colejohnson66]

Why would the heap make memory usage unpredictable? How’s it any different than the stack? For example, if I stack allocate 1000 bytes, leaving the function frees those bytes (by destroying the frame). If I allocate those 1000 bytes on the heap instead and make sure to free() it, there’s no change to memory usage.

[Dylan16807]

It's easier to figure out what calls what and the maximum stack depth of some or all of the program. Trying to track maximum usage based on allocations is a lot harder, especially when you have to deal with fragmentation.