Ask HN: Paste and keep source formatting, legitimate use cases?

I was just writing an email in Gmail and pasted an order number into the email which was copied from another website, the order number text was bold and massive which didnt match the rest of the text.

Can someone please explain a legitimate use case for the _default_ functionality on applications like Word, Excel, Gmail & numerous popular note taking apps to keep the source formatting? It seems to _always_ be more annoying than useful.