Considering how terrible almost everyone seems to be at measuring things generally, or at setting up the conditions for meaningful measurement, or getting buy-in for more effective measurements because they come at some cost and “what Jim’s been doing seems fine” (it absolutely is not) I’m skeptical that advertising folks are somehow much better at this than everyone else, and if they’re not a lot better then they’re still fairly bad.
Actually I always found it quite difficult to measure.
Mainly because selling B2B the person who clicked the ad is rarely the person who raises an order. I can use a proxy like instigating a download but that is far from perfect.