[JJ_SO]

Contrary to Sigma's engineers I don't know. Given there's no other brand doing this kind of "bugfix"-help, I find your comment aiming to be called "stupid", too I don't because that would be impolite to one of the hosts and also not necessary. LIke most accessories, one can take pictures without them.

 

As soon as I really know which part of a defocus issue on some distances comes from the camera's itself (then Sigma would bugfix the camera's manufacturers inaccuracies) or their own lens isn't manufactured without flaws. And given their quality, I sort of doubt the last bit. For a lens supplier this is the way not to be locked out by camera manufacturers "developments" to make their mounts difficult to handle to a competitor.

 

A USB socket in each lens

• would increase the costs of each lens - even the ones whose owners never want to do adjustments
  
• tempt people to use it the wrong way
  
• might be difficult to be placed in a already packed design
  
• is a very good way to bring humidity and dust into the lens
  
• most probably would interfere the interaction of camera's AF and lens's AF drive unit
  

This are the reasons I could think of and maybe I miss the main reason. But Sigma would answer your question better than me, I guess. It even could be that the camera manufacturers own lenses adapt to their cameras with a silent firmware upgrade of the lens. And what's so bad about bugfixing? Never made a firmware update for some camera? I can only speak for Nikon, but D800, D7000, D7100 and even D5100 had other firmware versions when I bought them. And there were not more versions of firmware coming from Sigma, but at least for the 35/1.4 that was an improvement of faster although more precise AF. Thanks to the dock it was done in a few minutes instead of sending in and wait to get it back.

 

I'm also not too happy about the handling but nobody needs to buy it to make the lens work at all. They also could have included  some sort of lens calibration module into their software. Like LensAlign which comes with focus target for 80 or 100 US$

 

Usually they are without flaws out of the box, after 100% check in Sigma's factory. Now one can finetune AF accuracy in 4 different distances at four different focal lengths and also finetune AF speed/accuracy correlations and shake reduction behavior. If one wants to do so. And I read rumours about making the dock work also for elder Sigma designs. I don't call that only bug fixing and I don't think it should be free, especially because Sigma's import service gives lifetime lens-check and cleaning once a year for free here in Switzerland. Sigma even offers a mount change although not for free.

 

Are you aware of any camera manufacturer doing anything for free after warranty is over?