Just to nit-pick: This will depend on the settings of ANSI_NULL_DEFAULT_OFF / ANSI_NULL_DEFAULT_ON for the session, or by the ANSI_NULL_DEFAULT database option. By default, these will be set such that columns that don't have nullability specified will allow NULLs.
As an application developer, I would have wished this to not be the case. Unnecessary NULLs have been the bane of my existence.
Just because you're right doesn't mean everybody else is wrong.