This is neither related to SKick, as - again - SKick maps the ROM to RAM, though with relocation information - but mapping a compressed image to some place makes neither sense.
How is it not related? Both load the kickstart from somewhere into RAM, whether it's from floppy, hard drive or a compressed ROM. I'm not sure I'd bother compressing it into ROM, but I have and would load a kickstart from floppy and hard drive.
One way or another, this is not a good option. It requires more RAM, not just the decompressor, and as most users use hard disks anyhow, it is much simpler to load the modules missing in ROM from harddisk instead. It also makes the kickstart more flexible.
It's a good option if you want to be able to load different kickstarts but don't have an MMU or hardware that lets you load kickstart from disk in another way. It's more flexible than being limited to one version of kickstart.
For the limited use case that you are arguing against then I agree, but that doesn't mean that I wouldn't load kickstart into RAM in other situations.