- You cannot get the native address of arrays in order to pass them to native code.

- Arrays are subject to being moved by the GC, so even if you could get the address they could move.

- Arrays are limited to around 16 GB, and that's if you're packing data into longs.

- Accessing an array involves a bounds check, which may float out of a loop, but may well not.

- Arrays cannot be allocated with memory that is anything except mapped private.

I use Unsafe to put memory into a location where I can get a stable native address in order to make native calls using it. Using an array would not allow that.