It matters here in the sense that to show the poles, you need to stretch the Mercator map to infinity, because the function sec(x) is undefined at 90 degrees. This is clearly absurd, so map makers get around the problem by cutting the top of the map off, usually around the 85 degrees parallel. I chose not to include this detail in the article.

To slightly misquote the great Richard Feynman, "It turns out that it's possible to sweep the infinities under the rug by a certain crude skill." :)