Maybe a little bit less sinister than that. Just a way to promote the product in every email originating from their devices

Regardless of the reason, I think less of anyone who doesn't turn it off. Made me cringe so badly when I sent an email from a new email client that added something similar and I hadn't checked the signature.

One reason I feel that way is that the only time I'd see it in a work context is if it's a phishing email.

I see it all the time in a work context. At three different jobs.

No one really cares where I’m at. I have my laptop signature set to:

    Thanks,
    Kayodé
    
    $NAME
    $RANK
    $SERIALNUMBER

I leave it there even if using “Thanks” isn’t entirely correct and my name is repeated below it. Everyone else here does something similar.

My phone signature is the iPhone default. Just like everyone else.

The Blackberry had “Sent via Blackberry” before iPhones exsisted.

Or more simply to convey "I sent this email while on the go so without access to my pc/office/documents/files/etc". Gives important context.