It does make me wonder though, what happened to plain text emails? I had to abandon my favourite email client (mutt) purely because I received too many html emails. And I'm not just talking about marketing emails. Those I don't care about. I'm talking about work emails from colleagues.
Converting from HTML to text isn't that difficult, there are a number of open source libraries that'll do it. The harder problem is if someone sends you an email with a lot of images or where the layout of content is important, which is why people typically use HTML, it's much harder to map those aspects to plain text.
Every time I get a crappy text version of an email, I try to contact the company (via email or Twitter) to get them to care about text emails. Usually, I've received encouraging replies. It seems like marketing email services don't optimise text versions and companies don't even realise that. Probably because fewer people care about text versions.
I encourage you too, to send requests for better text emails if you care about this.