Although you may have a fast 20Mbps connection, it doesn't necessarily follow that the server you're accessing, and which could have a considerable number of simultaneous connections, can deliver web pages at the full potential of your connection.
Bear in mind also that many websites that you view contain adverts, so you have to retrieve the ads from these servers too.
Then there is the process of resolving the web pages in your PC. My connection was recently increased from 4Mbps to 10Mbps and I cannot see any significant speed increase in loading web pages. File downloads can be faster and utilise the full 10Mbps bandwidth, but again it depends on the ability of the host server to deliver the data.