This is a really great question.
I came from G29 to your current wished for set up. More recently, I replaced the CSL elite with the F1 DD1 (but changeover to a GT style wheel/ rim). I also play GTS 99% of the time.
Answer: People playing Gran Turismo tend to use ABS exclusively. They also tend to use the racing compound tires instead of tires appropriate for the car. For these reasons I think your question has merit that maybe the high-end equipment is not really [as] useful in GTS. At least that’s what I’ve found. But then I can tell you for the enjoyment factor I still think it’s worth it (although I have to deal with the frustrations as mentioned above).
Oh yeah, please check the link in my signature as to what GTS is. It may also have some interesting tidbits for you.