Why do sales people get commissions and engineers don't? Because the sales person knows exactly how much money they bring in and can claim "if I didn't make the sale, that money would not be coming in" even though it's not always true it's a good story. An engineers actions are so far removed from revenue that they can't make a claim so directly. Also, if they did want to claim a portion of product revenue they could…
It's more likely to be because in sales, the individual can have a major effect on the numbers that their commission is calculated on, so (as the article describes) that attracts the strongest performers, because they know that they will be well-compensated.
In positions where your personal performance doesn't have a direct and immediate effect on the numbers, the strongest performers won't be attracted to commissions. If you were part of a software development team would you want a significant part of your compensation to be at-risk based on this quarter's sales numbers? Probably not, because you know that you could bust your ass this quarter getting an important release out but still see your paycheck dive because that big potential lead backed out of signing.