Windows install media was done with CD/DVDs long before USBs. Further, burning a CD/DVD, including a self booting install CD/DVD, from an ISO is so common place, since Windows 7 it is natively supported (no third party utility is necessary). As I described above, insert your DVD, right click on the ISO file and it will burn the ISO to a DVD and if it is a bootable install media ISO, such as a Windows 10 ISO, the DVD will boot up when you start your computer and install Windows 10.
With Windows 10, nor previous Windows version, there is no native support for creating a bootable USB from an ISO, hence a third party utility such as rufus is necessary. But making a bootable install DVD is easily done, pretty much always works, and often works better, though a bit slower, than a USB.