because AC in reality is not a drift platform.
categorically false, it is a driving simulator. drifting is a driving technique, inherently you drift every time you go through a corner with controlled oversteer. if you could not drift in ac, it would not be a driving simulator.
ac gave us drift versions of cars, and their version of motorland sp. why, if not because the same platform thats so great for racing is also great for drifting? the fun that can be had in these cars speaks for itself.
some like to drift competitively, where there is a combination of objective and subjective judging of the drivers runs. typically this is only done in organized competitions.
as you seem to have noticed, the majority like to drift because they like to drift. to get on a server and tandem with friends and strangers. the same reason others may want to have an intense race at a legendary track, or cruise a highway with dense traffic on an open world map, or just lap the nordschleife in street cars for hours.
this open-ended nature, which has come from both the base game and mods made for it, is what propelled ac into its position as one of the greatest simulators of our time
and yes, just like competitive racing, and its equivalent of casual track days, drifting is a firmly established branch of motorsport, with professional industry-sponsored competition for around 30 years. no amount of reductionism can get past this objective fact.
a point system would do little for the community you seem to have some sort of emotional reaction to, because the majority aren't drifting for points, they are drifting for fun, the same fun that i hope you have doing whatever it is you play AC for.
the open ended nature of AC is what keeps it popular, keeps money in kunos' pockets, and therefore brings us continued development and releases from them.
to make this non-statement about something you don't seem to understand at all, and assume it would bring value to a sequel is... odd