The true tl;dr is this: hours are meta-information. Just like 5am is very early in every time zone, 11pm is late. We expect businesses to be open from 8-11 to 16-19, just like we expect everybody to be awake between 11-21.
Now, remove that bit of metadata and we need to figure out how to encode/transmit it again. At the end of the day, we just recreate time zones, with the added downside of removing a common language we have while traveling - Visit SF from the UK and not only are you jetlagged, but you need to remember that every time of the day you're used to needs to be shifted by 8 hours. - and just... talking to people in other time zones.
Right now, if you post a story on HN about needing to get up for work at 4:30am, everybody will understand: this person gets up for work really early! Move to UTC and it means nothing.
Now, remove that bit of metadata and we need to figure out how to encode/transmit it again. At the end of the day, we just recreate time zones, with the added downside of removing a common language we have while traveling - Visit SF from the UK and not only are you jetlagged, but you need to remember that every time of the day you're used to needs to be shifted by 8 hours. - and just... talking to people in other time zones.
Right now, if you post a story on HN about needing to get up for work at 4:30am, everybody will understand: this person gets up for work really early! Move to UTC and it means nothing.