Just as a counter to your assertions - the code base I work on at work has its own memory allocation in it. It isn't the same as malloc, because all memory is allocated up front (and done by the caller, not the callee). There are no gaps in the memory (aside from those for aligning things nicely) and there is not really any way that you could make the memory usage any better in these regards (e.g. it is dense, and there is zero overhead after initialisation).

Garbage collected languages prevent this sort of thing from working, because they force overhead, and even though they might be able to do better than a lazy programmer, a person who cares about what they are doing will do ok.