It would be impossible to create a single kernel binary image that would suit all the hardware configurations out there. Instead, kernel supports the initrd. initrd is a virtual file-system that contains drivers (kernel modules) needed to boot the system. For instance, very often a SCSI controllers drivers reside inside of the initrd. Kernel needs a SCSI controller driver to boot the operating system, but it does not include it, nor it can read it from hard-disk (you’d need a driver for the hard-disk, right?). And this is when the initrd becomes very handy.
To extract the content of initrd file, use the following command:
gunzip < initrd-18.104.22.168-0.1-desktop | cpio -i --make-directories