Adding the option to force an attribute to store a certain case of letters (uppercase or lowercase) while importing will be very helpful with a scenario where the customer needs only a certain one in an attribute (e-mail address for example). So, whatever the value stored in the file being imported it will be automatically converted into the default value defined (either upper or lower case).

======

Case scenario:
A customer is importing from two different sources where the e-mail address is saved in uppercase in one source and in lowercase in the other. So, the attribute kept updated on every import (once to uppercase then to lowercase). Hence, the customer wanted to set the attribute value to be stored only in lowercase so these imports won't make any change to the database anymore (as they will always be stored in lowercase anyway).