Second, U2F is not about USB sticks only. It is a protocol that works over NFC or Bluetooth. Soon it will also be possible to use your phone as a U2F authenticator for your laptop.
Third, how is it not adoption when Facebook, Github, Dropbox, Google and many others have added it.
Forth, a lot of hardware already has support built in. Lenovo laptops, Samsung phones and so on. Android has added an API. The new Snapdragon chips have it implemented on a very low level that will allow key storage in a secure enclave with dedicated transport to the finger print reader for example.
Five, where are you getting this 19$? You can get sticks for as low as 5$.
When is the last time authentication technology has been adopted like that? I would think never.
Google has published a paper about their experience, https://www.yubico.com/2016/02/use-of-fido-u2f-security-keys...