I think the super cars are awesome!!
GT5 & 6 have been out for how long now? Can only drift the same slow as Silvia for so long before it gets old.
If real world drifters were free from the worry of damaging their car and paying for rebuilds like we are in the virtual world, I absolutely, 100% gaurentee you would see people drifting super cars all day, err'day. Cost is a factor in real life, not a factor in the game...so why'll allow it to limit your experience?
Lastly, due to the limited tuning/customization in GT, there are things you can do with super cars that you simply can not do with a low horse powered, bicycle tired car. Yes, we all know we can tandem S-chassis...but with supercars, everything happens at a much faster pace, so you have to be that much more on your toes. It's just another way to challenge yourself. I enjoy drifting my LFA as much as I enjoy drifting my AE86s.
(Also, most of the good JDM drift cars are standards, and that bugs a lot of people. Many people completely dismiss them...not my way of doings things, but I understand why some people do it)