Whenever one uses universal time or local time they still have to calculate (or look up some table) before they can consider whenever it's day or night in some unfamiliar remote place.
Universal time system solves the problem of discussing time. It works when you're talking to a person, negotiating time of some event - you can both be sure that you use same notion of time.
It's especially good if notation radically differs from usual HH:MM:SS (like swatch @BBBB), as one can accidentally misassociate time systems in their head.
So use UTC instead. It is already there, your computer, phone and alarm clock can already handle it, and the issues of leap seconds, leap years, a changing length of day and accurate time keeping have already been addressed.
But the world still spins regardless of how you end up talking about time - you will still need to figure out the human behaviour at the specific location on earth at that specific time. It is useless to schedule a conference call when the participants are all in bed. SUT does not solve this problem - people will still need to take into account the fact that night and day still exist and most people work during daylight hours.
It solves a problem which does not exist - people organise things based on an agreed timezone already. The pain of transitioning to SUT is not worth the (debatable) gains.
Actually I don't agree with you - I think if humans got used to SUT, they can (in their own time!) easily recognise the shifts around the globe. I.e. 2:00 SUT is the start of the day in Europe, 5:00 SUT is start of the day in US and 7:00 SUT in Asia.
I believe that due to talking about the same time, people can more easy remember the other times.
Compared to time zones, which are based on learning them by heart without a relation to your current time zone (only relates to UTC and your time zone to UTC again -> 2 calculations).
Yes, but you're missing the point - people talk about the time of day, almost universally in relation to the standard 9-5 working pattern that most of the industrialised world follows.
What does 'this morning' mean in SUT? 'This evening'? 'I'll speak to you tomorrow'?
Universal time system solves the problem of discussing time. It works when you're talking to a person, negotiating time of some event - you can both be sure that you use same notion of time.
It's especially good if notation radically differs from usual HH:MM:SS (like swatch @BBBB), as one can accidentally misassociate time systems in their head.