From the article:

The uncontrolled exposure of this information,” says Narseo Vallina-Rodríguez, researcher at Imdea Networks and co-author, “allows advertising services or spy applications to create a digital fingerprint of your home that uniquely identifies it or can infer your income level and habits.” Not only that, if these devices scan for new information frequently “they can infer who enters and leaves the house and your social structures to monitor their activities through networks and devices,” adds the expert.

…

For example, this data is captured by apps that we carry on our phones and they collect the serial number of the router or the name of the connection, which allows us to know the location (without even accessing the device’s GPS). There are pages where Wi-Fis from all over the world are mapped. If two mobile phones access the same Wi-Fi, you not only know that they are close, but also where they are. If an app on the visitor’s mobile scans how many smart devices are there, and which ones, that data can help calculate the household income of that home.

Cybercriminals target high value individuals with attacks ranging from phishing exploits to ransomware. They use sex as a lure. This is all over the news. The idea they wouldn’t use data of this sort for blackmail because ’ it’s too much work’ is folly.

I cited a UN report on cybercrime in this thread.