They can be, though I do believe the release engineering team should first look into why they are consuming so much space. As a comparison, OpenBSD has a vastly larger base than FreeBSD (includes Xserver, drm drivers, web server, perl, etc). And yet they still manage an installation CD that fits on an actual CD.I have multiple times suggested that the OLD CD image and DVD image size limitations too be abandoned.
So whilst it is easy to just use a DVD or memory stick image of 8GB there is still clearly a bug in the release engineering.