We have slackbots that post, for instance, who has vecation every day. Because it is configured to post this using UTC, the time of day this is posted changes twice a year.
I might have a recurring appointment for lunch in my calendar every day at noon. Now DST happened, so I have to wait until one to eat. That is inconsistent to me.
Timezones change. If I have to go to the theatre on half a year at 18:00, I don’t want to be there at 19:00 because someone decided local time would be better if we moved it an hour. The show time certainly won’t be moved.
What is local time? It’s spacetime. When did it happen and if relevant (eg. a photo) what was the offset (because I would like to know the time of day)? When will it happen, and where? Online meetings across timezones are tricky, of course, but excluding the timezone won’t improve that.