Ask HN: Why has there not been large scale adoption of digital pens?

There's been many on the market for a while now, have you used or considering using one? What has your experience with them been.

Probably the most famous, consumer facing firm that makes digital pens is LiveScribe:

http://store.livescribe.com/

Equil Jot 2, funded on Indiegogo I believe, just came out to mixed reviews:

http://www.myequil.com/

And there are several others on the market. Why do you think adoption of digital pens has not really taken of en masse? Is the technology not good enough? Do people just prefer using laptops/tablets/phones?