You can choose to not install applications that use birthDate. It’s your system.
But, you cannot choose what other people want to install. It’s their system.
There are applications which exist, that other people can choose to install, that require this field and systemd is the logical place to store that information.
If you don’t like the applications that would use this field, and you don’t want your system to store information in birthDate then there is absolutely nothing stopping you from doing that. You don’t get to make that choice for other people, however.
You can choose to not install applications that use birthDate. It’s your system.
But, you cannot choose what other people want to install. It’s their system.
There are applications which exist, that other people can choose to install, that require this field and systemd is the logical place to store that information.
If you don’t like the applications that would use this field, and you don’t want your system to store information in birthDate then there is absolutely nothing stopping you from doing that. You don’t get to make that choice for other people, however.