When you write, you’re selling something!

When you write, you’re selling something:

A story.
A belief system.
A product.

Your marketing copy sells your product.
Your UX writing continues selling it.

Good UX copy affirms our decision to buy your product. It makes it enjoyable and satisfying to use, ensuring we keep using and paying for it. We then become walking advertisements every time we tweet about your product or recommend it to a friend.

And so, the same writing principles you'd apply to advertising or marketing can be valuable here.