Unfair on some, perhaps, but in my experience the people who only do an FI rating as a last resort, a year aftet their CPL/IR and no airline interviews, usually make lousy instructors.
I'm not saying I'm the best in the biz, but I did CPL then FI, and got straight into instructing, as I am passionate about light aircraft. I know instructors who fly PA28s and PA38s and don't really know or understand the differences in their engines. It just shows a lack of passion about the subject you are teaching.
This may not be fair on some instructors, but it's definately not fair on the student who ends up getting taught to fly by them.