Well, I think of two things:
- With columns I could sort up-/downwards.
- The view should be comparable to explorer view, and in explorer you have such a column.
Another thing would be that in theory, you can define one file type with multiple possible extensions. A real file type column, would group these different extensions together, because of there definition. So a real file type support would be nice for someone, who keep an eye on the defined file types of his/her system. For the average user, file type will be just equal to extension...
P.s.: I agree with you. Because you can actual sort, this has a very low priority.