For one thing, allocating every object on the heap leads to a lot of cache misses because the data you're working with is not contiguous in memory. It may also

For one thing, allocating every object on the heap leads to a lot of cache misses because the data you're working with is not contiguous in memory. It may also make it harder for the CPU to do speculative fetches from memory because it needs to resolve the value of a pointer before it knows where to fetch data. With the stack, the address is much more obvious since it's all constant offsets relative to the frame pointer. Also, heap allocation is unpredictable. It is more likely to cause unexpected page faults or thread congestion (multiple threads often share the same heap so they need to synchronize access to memory book-keeping structures). Especially when it comes to kernel drivers, a page fault can lead to a deadlock, infinite recursion, or timeouts. I'm not saying heap is always bad, not even that it's bad most of the time. But if a language doesn't at least give you the _option_ of having objects live on the stack, I wouldn't consider it a serious systems programming language.