Let me rephrase. HTML email is often required due to the requirements of the marketing department at many companies.
As for "look better" - yes, it is subjective. However, given that html email capabilities are a super set of text email capabilities, anything you can do in a text email you can do in an html email. Anything you can do in an html email, though, you cannot necessarily do in a text email. Quite simply, an html email can look better and often does.
Edit: Given that an email can contain both text and html versions, and given that best practices dictate sending both, is this not good enough? You can always set your client to show you the text version by preference. You get your text version, most everyone else gets the html version.
As for "look better" - yes, it is subjective. However, given that html email capabilities are a super set of text email capabilities, anything you can do in a text email you can do in an html email. Anything you can do in an html email, though, you cannot necessarily do in a text email. Quite simply, an html email can look better and often does.
Edit: Given that an email can contain both text and html versions, and given that best practices dictate sending both, is this not good enough? You can always set your client to show you the text version by preference. You get your text version, most everyone else gets the html version.