Display advertising will show you products that you have expressed an interest in today.
Streaming video has ad slots similar to traditional linear TV because it's what people are used to. There is the opportunity to do much much more.
What I could see happening is content changing to be tailored to the viewer. This would both decrease subscriber churn in the increasingly competitive streaming space, as well as add a feature to advertise via the content itself.
You like the pants? Point your remote at them to purchase with a single click. Honestly, I could see Amazon sponsoring streaming content for that purpose. AWS has streaming services and Amazon has been doing the logistics for decades.