Blue and purple links wouldn't be visible on any website that chose to use those as background colors (or any range of background colors where the contrast would have been too low to be visible).

The web at the time was an "anything goes" multimedia format, not a dry digital paperback or textbook where all the content had to fit within the publisher's specifications to limit printing, weight and distribution costs.

Nowadays, most browsers have a "reading mode" that can flatten the content into something that satisfies those Nielsen conditions though.