There isn't actually much point in using initfs when you're on known hardware.

Initfs is mostly useful for traditional distributions where you have a generic kernel with most drivers as loadable modules. Then you boot from a ramdisk image (part of initfs), you do some hardware detection, you can then go on and load (from that same ramdisk) the drivers you'll need to access the actual root disk, e.g. scsi driver? or IDE driver? Or SATA driver? And filesystem driver: ext3? Reiserfs? and so on.

That way you can have a lean, mean kernel (due to drivers not compiled in, but being loadable modules), and load the drivers you need at runtime. Obviously that wouldn't be possible without initfs, because you can't store the disk (well, SD) and filesystem drivers on the root filesystem you haven't mounted yet.

However, when the hardware is known you simply compile in (as in 'part of the kernel, not dynamic, loadable') the minimum set of drivers you know you need (to be able to load the root filesystem), and you can skip the initfs step. (When I install a system on a desktop I usually make a new kernel for myself , without initfs).