What exactly do things like WebUSB and Web Bluetooth contribute to Google’s ad business?
(Except if you mean that any new and initially exclusive feature bolsters Chrome’s dominance further, in which case I’d somewhat agree.)
Google keeps proposing specifications like Web USB, Web Bluetooth, Web MIDI, Web Serial, etc., and both Mozilla and Apple keep shooting them down on privacy and security grounds. Meanwhile Google ignores the problems and builds them into Chrome anyway, and guess what happens? They start getting used to fingerprint and track people.
Who knows, maybe it’s just a coincidence that all of these technologies that advertisers can use to fingerprint and track people keep making their way into the browser owned by one of the world’s largest ad companies.
HID, mass storage devices etc. are required to be filtered by implementations, and why would I grant a random news or social media site access to my MiniDisc player, Arduino board, Bluetooth thermometer/hygrometer etc. when it asks for it?
The prompts are pretty scary/disruptive, and I've never seen any website actually try (unlike for e.g. web push notifications, which are fairly private but can be super annoying).
Part of the problem is that a vast number of users neither understand nor care about these prompts. They just click to make them go away.
There’s a few long discussions on the unsuitability of these specifications in the Mozilla standards positions repo:
Web Bluetooth: https://github.com/mozilla/standards-positions/issues/95
Web USB: https://github.com/mozilla/standards-positions/issues/100
Web MIDI: https://github.com/mozilla/standards-positions/issues/58
Web Serial: https://github.com/mozilla/standards-positions/issues/336
Here’s some Hacker News discussion about it: https://news.ycombinator.com/item?id=23679063
As far as fingerprinting/tracking goes, I have never seen a random site prompt for these features, only apps where it makes sense.