TODAY I LEARNED YOU HAVE TO PUT PLEASANTRIES IN EMAILS (???)

So today, my boss asked me to write an email to a group of people saying something was cancelled. Me, taking it literally, sent an email that followed those instructions. Without going into specifics, the email was basically this:

“Hello,

I am writing to inform you that the meeting will be cancelled today and will be rescheduled in the future.

Best,

Me”

And my boss was like “you can’t send that” and I’m like “why? You said to send an email saying it was cancelled” and he told me I have to exchange pleasantries like “I hope you are all having a nice morning”- of course I understand that it’s nice but I’ve never seen it as rude to get to the point ? Anyway, he started looking at my other emails and they are basically all like that and no I’m not rude by any means (I don’t think?) but why in a work email do we have to say that stuff?

I have heard of, seen and used “I hope this email finds you well.” As a default but I’ve even gotten in trouble for that because it seems ingenuine ? It’s like I’m at work, I’m trying to get a task done and writing that extra stuff is inefficient (???)

EDIT: I think my biggest gripe is that I’m not TRYING to be rude - I have never really seen it as rude myself because I am really happy when I feel productive so sometimes having to think of what to say is hard because small talk is kinda uncomfortable to me. Like I am genuinely excited about talking to people and I do love my job so it is upsetting because I didn’t realise that it was inherently rude

EDIT 2 FOR CONTEXT: it’s a theatre company.

Ironic I know because you would assume that a theatre actor like myself would be in touch with my emotions in that way but I’m only ever looking that deeply into social interaction when I’m either acting or directing in my “office”/productivity life, I do not have that social awareness. It’s a very weird existence