Recently we sold out of our Striped Maple jerseys so we marked them as no longer available in our store front and the pages became hidden in the store. If product pages are not current and public, any links to them (either somewhere on our website, such as here in the blog, or in social media or elsewhere on the web) will no longer go anywhere - they will fail with what’s known as a ‘404’, page not found.
No-one running a website likes to think that visitors to the site will see 404s if they can be avoided. There are a number of approaches that a site can take that (including leaving the product pages public, although I think that can still be frustrating when you see items that never have any stock).
We have set up a product archive page, where we’ll include a picture and a couple of lines about items that are no longer part of our current product lines.
This way we have somewhere to send visitors to the site who have followed a link to a product from the past. As new items are retired, we will add them to the page.