Perhaps because there's more to a camera than just the sensor alone? IIRC the main reasons for panning the earlier Sigma cameras had a lot to do with their ergonomics and responsiveness as picture taking machines and not much to do with the sensor performance.
|.....the ROYAL LOTUS 2017/08/25-NEW YORK..... by Chiwat|
from Wild flowers
|Coffee and Mango cake by clicker88|
from Another cup of coffee