Much like how in PHP with SQL, you have functions that can be used to safeguard your code from SQL injection, I believe it'd be useful to have a similar method available in SQF.
This way, data validation from publicvariable messages etc doesn't need to be so extensive to protect from script injection.
Yes, you can make your own SQF function that does this, sure, but an engine method would be MANY times faster, and would scale with future improvements, as the source for these script function names could be dynamically sourced etc.
As said above, there's no REAL need for such a function, as you can plug this hole with your own implementation of the function, or with data validation, but the simplicity of having a function that dictionary tests each word within a string would greatly cut down on the need to manually validate data entry.