Can you elaborate why?
I sometimes abuse this option by including screenshots in the body of e-mail, but I could as well add it as an attachment. Other than that I see no reason to use HTML in e-mail conversations at work.
Intra-corporate e-mail is often used as an ad hoc document collaboration tool.
"See my comments in blue", strikethroughs, inline diagrams, bullet points, big red font for emphasis.
Of course that should all be done in a dedicated application, but who is going to provision and authorise users for that versus just adding Bob to the cc line and giving him implicit editing capabilities?
The functional overloading of corporate e-mail is a user-driven reaction to the awfulness of most " collaborative' software.
I've always had my work email client set to text only. Never been a problem for me (unless you consider missing out on a lot of unnecessary smilies, fonts, and colors a problem).