I quote: "Warning: This image is oversized (which is a bug) and will not fit onto a standard 703MiB CD. However, you may still test it using a DVD, a USB drive, or a virtual machine."
Tangentially, there are still netinstall (mini.iso) and Lubuntu Alternate images (which allow to install a basic command-line system and go from there) with a text-based installer which DO fit on a CD.
http://cdimage.ubuntu.com/daily-live/current/
I quote: "Warning: This image is oversized (which is a bug) and will not fit onto a standard 703MiB CD. However, you may still test it using a DVD, a USB drive, or a virtual machine."
I guess it's not a high-priority bug then :)