The outside and inside edges of a track can be a bit of a mystery. Some tracks have very large aprons while others have dirt, grass, or even a slightly raised kerb. Going over a kerb at high speed can really unsettle a car and cause it to oversteer quickly. Clever drivers sometimes take advantage of this, but it’s not without some risk. In the first clip, a Miata driver encounters the T6 inside kerb at Laguna Seca (I mean Mazda Raceway), loses control, and collects the POV car.
In this next clip, there is a low apron on the inside of T7 at Lime Rock. The leading edge of an apron can get dug out from being driven over repeatedly. Driving over a dip is a lot like driving over a kerb. In the following video, the driver is really unprepared for the sudden oversteer and his corrections are unpracticed and uncoordinated. Un-good.
Streets often have kerbs. It would be idiotic to race on public streets, both because it is illegal and because you could damage your car hitting a kerb (not to mention a light post, pedestrian, dog, etc). While a closed parking lot can make a convenient autocross course, it’s a stupid sort of convenience.