And it is weak because people are different. Some people tolerate clock change better than others, some people function better in summer time, others function better in winter time. Any decision you make (keep clock change, summer time only, winter time only) will benefit some people and will hurt others. And there is not even strong evidence that one solution is better on average.
For the disruption caused by clock change itself, it is indeed noticeable, like an increase in traffic accidents, but it is just one day, but the effect of being in summer time vs winter time lasts 6 months. So if the clock change makes even a small improvement for 6 months, it may be worth the disruption for 2 days a year. I am not saying there is, it is just that there is no real consensus.
So, by default, when a change may have negative consequence for some people and may not lead to an overall improvement, you don't change.
This is a very European / North American problem for some reason. There are some exceptions, but in general Asia, Africa and South America don't do this.
If you mean "changing the rules a few hours / days before they should be applied", Chile (again) did this a few years / decades ago, and it wreaked havoc: all scheduled meetings were off by one or two hours, you could not rely on your calendar, etc.
Plenty of stupidity going around in Chile / South America, rest assured.
Nope, only Chile, and not even the whole Chile. Similarly, Egypt is the only exception in Africa, Lebanon/Palestine/Israel are the only exceptions in Asia, plus also New Zealand and like half of Australia.
The vast, vast majority of the world including China, India, Mexico, Russia, Iran, Turkey and so on don't move their clocks. In fact, out of 20 most populous countries in the world, only three do: United States, Egypt and Germany.
This is surely an exaggeration.
https://ec.europa.eu/commission/presscorner/detail/en/ip_18_...
How would something that has been in effect for at least 60 years still lead to a worsening mental state over time?
https://aasm.org/advocacy/position-statements/daylight-savin...
The transition from daylight saving time to standard time leads to depressions https://clin.au.dk/display/artikel/the-transition-from-dayli...