I used to get full challenge treatment, but then I realized, I don't drive like that at all in real life. So I leave ABS and traction control on at the lowest level, exactly like my real-life Subaru STI currently sitting in my garage that I often took to Laguna Seca and local events.
In real life, traction control and ABS saved me from repair shop countless times. I just try to replicate the car as closely relate to what I pull out from my garage as much as I can. Theoretically, you still can get very good lap time driving at the edge of your ABS/Traction limit. Most new cars nowaday can't even turn off ABS without physically removing the hardware. Unless, you have an old BMW M2, then it is in a menu on your screen.
While I understand where you're coming from, it all just comes down to confidence and ability. I've been practicing car control, doing track days and drifting for many years now, and don't want levels of control taken from me.
For instance, I was tracking my cousins Cadillac ATS-V last year and before one session we had forgot to turn the TC fully off (it has multiple levels). When I pushed the car into oversteer through a left hand corner the car violently cut power at a pretty good angle forcing me to then recover from something unexpected. It was fine, but if I had turned it off like I should have that turn would have been a satisfying drift, but it ended up being an ugly, slow tank-slapper. The car has to be stopped to turn it completely off, so a couple laps were done with it on so then I had to cut back on my limits to fall under the threshold where TC would intervene. It slowed us down a lot, and stepped in frequently when I still had complete control of the car.
Car control is not a mystery, in real life or this game. Top players prove that TC is a hindrance to ultimate speed and control. In the moments it's ever accidentally been on in the game I notice it immediately because it's screwing with my throttle inputs. My right foot is conditioned to be my traction control, and even though I know there are some really great modern TC systems out there, they don't beat me doing it myself.
Sure, on the street I don't bother to turn it off in my S6, but if I'm driving it spiritedly on a back road it's off, and I have the ability to control it well outside of traction limits... and would do the same in your excellent WRX. My own Impreza sees more dirt than pavement and I keep it as loose as possible when possible, and I pulled the ABS fuse out of it a looong time ago. My RX7 doesn't even know what traction control is, haha.
I appreciate where people are coming from when they use TC, and want for everyone to use it if they choose to, but I don't need or want it. It is a barrier to me gaining ability and having fun. Car control IRL and in game is a skillset to be learned, and if there are artificial things getting in the way of what you're doing it's much harder to reach your true limits.
) to get my fastest non-bugged 600pp car to win here. 
