I think this is because sales tends to be a one-person job in most settings (except the very highest value deals). One sales person manages a number of accounts

I think this is because sales tends to be a one-person job in most settings (except the very highest value deals). One sales person manages a number of accounts. Measuring the results of that person is then quite straightforward. Tech tends to be a collaborative job even in quite simple settings, which makes it immediately more difficult to measure. Add to that that the true results are often only visible after months if not years of work and you have a real challenge at hand. But I agree: there are also simple settings where you can measure a programmer’s productivity. Those are probably just not the settings in which people are that concerned about attracting top talents, though