One advantage of not supporting paging is that it gets the disk driver and file system out of the kernel. They're not needed early. You need a boot loader that can load the OS and process images, so the OS starts with some processes running. The disk driver (if any) comes in that way, rather than as part of the kernel.

QNX works like this. It's convenient for embedded systems, where you may have no disk at all, ROM, flash, or a hard disk.