A changing landscape, increased 'link rot' (digital decay, careful: article is titled Error 404): "The internet is stitched together by an incalculable number of hyperlinks, but much like cells in an organism, the sources and destinations have a finite lifespan. Essentially, links can and do die." (Nick Routley on Visual Capitalist; John Bowers, Harvard LIL)
"The Million Dollar Homepage lives on as a perfect record of that wacky time in internet history – or so it seems. However, the reality is that many of the hyperlinks on the canvas are now redirects that send incoming users to other sites, while over 20% of them are simply dead."
This is more worrying than you may think, e.g. 49% of the hyperlinks in US Supreme Court decisions are now broken [Yale study, pdf], or - worse still - many of the links in blog-posts from the 12 year Owsblog archive are now unreachable too :-(