I also had that But the experience is way worse than reading email in html format. And these days, almost all emails are in html format with pretty basic text/plain in the form of multiformat.

That plain text doesn't have the intention of the composer, for instance, the inline image doesn't show inline and the email context says the figure above.

It is not that business form, but some ppl use colorful format to emphasize some text, which basically gives same text in the email, which makes the reader (in plain text) easily miss that part while skimming.