For those that also live in the 21st century, yes. Which mail clients don't render HTML? Perhaps the users who still use ancient mail clients should consider switching, or endure reading HTML. I'm not going optimize for the minority by making web sites in plain text either for the few users who refuse to use a web browser.
Link rot, link hijack, it takes longer to reach the page, additional point of failure and domain based algorithms break. In other words, plague.