SSHFS and nodev

Tracked down a small problem this evening that had been confusing me for a while — I had been unable to mount or burn ISO images that were being served over SSHFS.

It seems I needed to add dev to the mount options. However, this still confuses me: why doesn’t the loop device see the ISO file as just a regular file instead of a “character or block special device” which the (previously enabled) nodev switch disables?