What purpose does compaction serve in a 64 bit virtual address space on Intel? The processor addresses and caches by cache line and the address space is huge

What purpose does compaction serve in a 64 bit virtual address space on Intel? The processor addresses and caches by cache line and the address space is huge enough to handle most allocations. Not to say it’s impossible in C/C++, but I’ve only ever seen fragmentation issues in old versions of Java and C# where the runtime repeatedly commits large swathes of contiguous memory. The key differentiator here is the VM’s insistence on contiguous allocations, whereas malloc has no such requirements.