[msla]

NULL is inevitable if you use JOINs, simply as a matter of what a JOIN is.

More deeply, NULL is inevitable because reality is messy and your database can't decline to deal with it just because it's messy. You want to model titles, with prenomials and postnomials, and then generate full salutations using that data? Well, some people don't have postnomials, at the very least, so even if you never store NULLs you're going to get them as a result of the JOIN you use to make the salutation.

You can remove the specific NULL value, but you can't remove the fact "Not Applicable"/"Unknown" is very often a valid "value" for things in reality, and a database has to deal with that.