The difference is that when people build on cutting edge tech that just about everyone agrees will be standard eventually they help push the advancement of that technology, when people built for IE only they used tech just about everyone agreed was horrible, caused vendor lock-in and was a huge security risk. I think if it works on Chrome, Firefox, IE 10, Windows, Linux, Mac, iOS and Android, we're pretty clear of vendor lock-in.
Guessing if things posted on HN will work in browsers and OSes I use (non provided by Apple, for highly ethical reasons) is a daily game of chance.
Is that really what we want? Is that the future we want? Wasn't this what we all shunned Microsoft for doing?