Because the HRE wheels look 10 times better than all the wheels you've mentioned . The price is steep but then these aren't your average aftermarket wheels....which weigh in about 8Kg. However recently realised that Enkai do a wheel (RFP01) that also weighs 8kg in alloy (18x9 only fitment for S5) which would be ideal for track work. ...£378 each
...for the street, the 20x9.5 OZ Ultraleggaras are about 10.5Kg (£375 each) in alloy and the BBS CKs are about 11.0Kg (£365 each) in alloy.
...so I've been wondering why I should spend £6,500 on a set of Dymags? - or now HRE??