In the immortal words of Marlo Stanfield: "You want it to be one way. But it's the other way."
Whether you like it or not, most business emails will be sent in HTML. People want it to look nice, people want to be able to put links in their emails so recipients can click through and they make money, they want to put tracking codes, etc.
Regardless of anyone's personal preference, emails will be in HTML for a long, long time.
