For anyone currently using a GUI mail client where HTML mail works out of the box, this is not something they will spend time figuring out before concluding that HTML mails just don't work. And this is a complete non-starter for those who like Mutt on the basis of having something that also works in non-graphical environments.
That's fair enough, but this is why I'm not recommending this to someone who is not willing to spend half a minute searching for this one-liner. I'd also wager that the intersection of such people with the people who would even consider using Mutt in the first place is basically empty.
My point is that if you don't have those two constraints, it's trivial to do and it works perfectly.
