Content creators (think Vox Media, whatever Verizon Media/the old Yahoo is going by these days, Reddit, BuzzFeed, etc.) have something to sell: impressions. Typically analytics tools are thought of from the advertiser perspective: people who want to get eyeballs on whatever product they have to sell. Publishers are on the other side of that dynamic often give away content for free, and their product is in fact the ad space served up alongside that content. This can be counterintuitive. This ad space from publishers is sold in two ways:
Transactional (via a marketplace)
Enterprise (large commitments directly from advertisers)