This is a more philosophical question, but such questions are allowed here.
As we all know, there are various free project hosts. The common feature for probably all of them is the ability to link or even manage an external website.
My question is do you think there's actually a need for an external website?
A place such a GitHub lets the project's owners create a wiki with screenshots, etc. Nevertheless, places like Wikipedia's software infobox treat GitHub like a repository while expecting the official link to lead somewhere else.
Why? Maybe big projects don't want to rely on a third party like GitHub, but what about small projects?
Why having 2 identical websites, both with exactly the same information, manual, etc. (except one of them is called a repository)?
What should be better for marketing?
And should you choose an external website, should you not use the repository's wiki in order to avoid the aforementioned duplication?