Why must mandatory attributes have a default value.

When creating a new attribute and making it mandatory a default value must be selected. This defeats the purposes of a mandatory attribute.
In all other systems mandatory attributes are left blank to force the user to consider the options available and then select accordingly.
When a default value is pre-populated then the user can accept the default without any consideration of the options, and this then makes the mandatory option pointless.
This is causing the customers a lot of issues as regardless of the scripted methodology users can complete a form without being asked to consider an option and as such the wrong attribute values are being populated into forms.