If I want to book an appointment for April 12th 2027 at 2:00pm, then that's the time I want.
If my locale decides in 2026 to opt out of daylight savings time and not use it anymore -- it does not mean my appointment is now at 1:00pm instead. My appointment is still at April 12th 2027 at 2:00pm. But if I had saved it as a prediction of a UTC time in ISO 8601, then the system would think my appointment was now at 1:00pm.
This is why it has to do with dates being in the future. A past date-time can be converted to a UTC time represneted in ISO8601 that will not ever change (if it was converted properly).
I'm not sure where you got restaurants from -- you are the first person in this thread to mention restaurants? That is one use case for storing dates and times in the future, but certainly not the only one! There are of course some where the time zone is not "obvious". You realize there is software that's used for things other than restaurant orders and reservations, right? (Also I can imagine a restaurant that's a mobile food truck in an area near a timezone border...)
You speak very authoritatively and combatively about something I think you may not be on the same page about.
I did mention booking a table, because I used to work with restaurant booking.
It is eye-opening to have not one but two devs challenge me, both seasoned accounts so probably experienced developers.
But I've dealt with the real problems it causes and they clearly have never touched future dates or they'd have already hit these problems. Or maybe the US's timezones are more stable than the EU's? I think between the two startups they had something like 2 million uniques a year, with bookings in the 100,000s, so not exactly huge scale either. And only operated in like 4 countries. But we still hit them.
And in the table example you don't need the "where", because it's obviously in the restaurant's timezone.