I still find it odd because I still associate third tier lens makers with still making third tier lenses and not out doing the big boys.
It is ingrained perception formed many decades ago when it was truer then it is now.
Cosina was Argus Cosina in the 1970s and not Voigtlander, certainly not Carl Zeiss ... and Sigma was a little better than Asanuma and house brands like Hanimex and Spiratone and maybe an equal of house brand Vivitar pre series 1, nothing more.
It is as simple as that really.