I use this when the tone of my email would otherwise be, where’s my spreadsheet motherfucker?? It’s nice to modify the overall tone of the email to something more friendly. I have a very curt writing style so I’m often concerned my emails will come off as blunt or demanding if I don’t include a pleasantry.
I work in a very friendly, informal field so I find myself doing little pleasantries to fit in, email-wise.
I think you’re answering your own question here.
Your blunt coworker has to explain himself or risks being taken as rude by people who don’t know him. You yourself couldn’t determine if he was being rude to you without some additional context.
Without further context, you don’t know how to interpret an email that says where is my spreadsheet motherfucker.
In both cases, you’re saying further social cues are needed to determine if someone you don’t know very well is being rude or not. Hence, why people emailing people they don’t know very well in a professional capacity include niceties to convey context and tone.