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'?
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).