Why not null values?

[burghard]

Fabrik is a professional content creation kit, which relies on database entries. I wonder why it is not possible to store null values into the database or leaving them intact when they are not changed at a form. Every time I edit a record, then all null values are replaced by a non null value.
Why there is no option to store or leave null values as they are if they are not changed in the form? I can not believe that nobody who is using fabrik ever missed it.