It’s far more flexible than something that just spits out an .iso image.

From the site:

“… create disk images that work in devices like BlueSCSI, Floppy Emu and PiSCSI / RaSCSI, as well as in emulators like Basilisk II and Mini vMac. The macOS version also analyzes images that either contain a single volume, or entire devices. It can show the contents of HFS, MFS and ProDOS partitions. And it can perform a few neat tricks like converting an existing image that works on Basilisk II into an image that works on BlueSCSI or PiSCSI / RaSCSI, or replacing your Lido SCSI driver by a classic driver that will improve performance in modern solutions.”

And you can’t boot into Mac System 6 directly off an .iso … just saying.