In the TV market, they were valued because the cable/broadcast/satellite services had no idea what frequency band users were paying attention to and thus no idea what was effective and what was not without some proactive examination of the viewer base. This was important for the program producers to value product placement, integrated advertising, and for the cable/satellite people to know what content was worth/not worth licensing.
For unicast streaming, the streaming service knows *precisely* what the users are paying attention to. For content producers, they control the licensing terms so they should be able to force Hulu, Amazon, and netflix to provide data as part of the deal of licensing it, in order to have data for soliciting things like product placement.
The streaming services themselves have all the data they need to entice advertisers that are independent of the content. Additionally, the advertisements are in no way hard linked to the streaming media. If the service wants to show you that ad, they don't need to give a rat's ass about *which* program you are watching.
Certainly the people providing the service know which pieces of content they license and how much they are watched to evaluate relative value of their library.
So the two remaining purposes are to let Amazon know which parts of Netflix library are valuable enough to fight for versus not bothering, and academic curiosity of the viewership. Of course, the former might be workable by requesting the data from the content owners as part of negotiations, and the latter doesn't really mean revenue...