Homer didn't need rich text to write the Trojan War. Neither did Shakespeare, nor Ovid for their writing. My emails are way less ambitioned and are fine written in poor text.
But, almost everyone does? Would you prefer all web articles to be strictly in plain text, same colour? No font changes between text and code, no colors for quotations, no indented multilevel bullet points? Basically, nothing that markdown can do. In your opinion, those things don’t improve ease of reading, right? What about syntax highlight in code - nobody needs that either, am I getting it right?
And how are emails any different from web articles? Both contain structured thoughts represented as structured text, both often contain code and quotations, lists and so on. Why special treatment?
For the sake of presenting marketing (Logos). Disgusting. Wear a mask, write text.