An interesting conspiracy theory [businessinsider.com] on Business Insider:
A Business Insider reader claiming to be a former ad tech executive at a really huge, well-known news publisher then sent me a fascinating email, in which he claimed that ad tech companies deliberately serve ads slowly because everyone makes more money that way.
Basically, his theory is, when a readers clicks to read a story, the page calls for bids from advertisers on the ad space available. This bidding is supposed to take place in a few milliseconds. But, my correspondent says, ad tech companies hold open the bids much, much longer, so more bids come in, driving up the price