Sometimes the default value for a given field just doesn't work for you. For example, you might want the default phone type to be mobile instead of landline, or you might not want to send an email confirmation by default when registering a new participant.
If that's the case - be sure to contact support! Most of these settings are not exposed via the user interface, but we can work some magic on the backend - either by changing the default field in the option table or by installing the configurabledefaults extension and setting the value there.