Why are these icons here?
Standards matter.
The WWW is based on open standards (HTTP, HTML, TCP/IP, etc.). The W3 Consortium exists to agree and propagate these standards. Verification of the quality of HTML in a web-page is important to maintaining an open WWW.
You will find that these pages are displayed by standards-conforming browsers equally nicely on a small phone as on a large monitor. Adherence to standards ensures this (and I have checked it!).
These pages should also be displayed nicely in text-only web browsers like w3m, lynx and elinks.
Time-stamp: "19-08-2015 12:47:18 /home/work/public_html/why-w3c-icon.html"