The python3 package should contain the entire python standard library
You are free to use a distro which does not split packages, favorite distro, Arch Linux (btw).
Or, you can install the recommended dependencies of python3. Testing in a container, the python3 package pulls:
root@a72bd55a3c1a:/# apt install python3
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following additional packages will be installed:
ca-certificates krb5-locales libexpat1 libgpm2 libgssapi-krb5-2 libk5crypto3
libkeyutils1 libkrb5-3 libkrb5support0 libncursesw6 libnsl2
libpython3-stdlib libpython3.11-minimal libpython3.11-stdlib libreadline8
libsqlite3-0 libssl3 libtirpc-common libtirpc3 media-types openssl
python3-minimal python3.11 python3.11-minimal readline-common
Suggested packages:
gpm krb5-doc krb5-user python3-doc python3-tk python3-venv python3.11-venv
python3.11-doc binutils binfmt-support readline-doc
The following NEW packages will be installed:
ca-certificates krb5-locales libexpat1 libgpm2 libgssapi-krb5-2 libk5crypto3
libkeyutils1 libkrb5-3 libkrb5support0 libncursesw6 libnsl2
libpython3-stdlib libpython3.11-minimal libpython3.11-stdlib libreadline8
libsqlite3-0 libssl3 libtirpc-common libtirpc3 media-types openssl python3
python3-minimal python3.11 python3.11-minimal readline-common
0 upgraded, 26 newly installed, 0 to remove and 18 not upgraded.
python3-venv python3.11-venv
I find it odd, because debian does this by default, actually. They account for usecases like yours, and instead you have to edit a config file or use a command line flag to get it to not install recommended dependencies.