because there are a lot of jurisdictions with laws prohibiting the concealed carry of a fixed blade knife with blade length over 3". Due to the various ways in which that 3" of blade can be measured, 2.5" or 2.75" is a simple solution.
That said - a 2.5" bladed Izula is a lot easier to use than a 2.5" bladed folder, easier to manipulate, and stronger. (and it still drops in a front pocket easily and comfortably)
as to what practical purpose?
lots.
cutting things around home, farm, office, mailroom, etc....
skinning small game, dressing out a deer, cutting up your steak at dinner, wood carving in your spare time, etc...