A "full" Debian installation media is 3 DVDs, or about 12 GB.
See here: https://cdimage.debian.org/debian-cd/current/amd64/iso-dvd/
Since this is quite inconvenient and an internet connection is pretty much ubiquitous, a more common installation media choice contains a significantly smaller set of packages. It only installs the base system and then establishes a connection to official Debian package repositories over the network. I guess you're using this type of installation media without a network connection.
If you finish the installation, note that you can request that screen again by running
tasksel as root. If you have added more installation sources since the installation itself (e.g., an Internet connection), you will then see the other options that should have been available during the installation.