If you have focus, if you're not aimlessly wandering around, ads try to distract you. They attack your personal agency and sovereignty, trying to divert you from what you were doing, to pay attention to what they're pushing.
Because they're in a zero sum competition, the dynamics are to escalate. There's only so much inventory, and the winners of the bids for your attention need to have more and more effect on your behavior to justify the escalating costs. Text isn't enough, images are needed. Images aren't enough, videos are needed. Videos aren't enough, interstitials with tiny close buttons are needed, with mandatory pauses. If advertisers could reach out and physically grab you by the head, they would.