Lefties left out.
Most Sigs are difficult for left handers, and with the exception of the SAO premium priced Sigs, Sig just doesn't care.
Since the Sigs do not have the barrel bushing lockup of the fabulous 1911, Sig barrel lockup is essentially no different than the truly fine S&W M&P, the Glock, the Beretta, etc.
Sigs fall into the premium priced arena. That means they cost more, but are no more accurate than the above mentioned guns. For my money a G17 will fire just as well as a Sig, cost less, and you can drop in better barrels and triggers for less cost.