Should 'www' be retired?

Ok, maybe this may be petty, but why do so many sites require that 'www' before the names? I have wasted lot sof time trying to navigate to sites by just their domain name, only to find out that I need the 'www'. What do I mean? Both of these should work:

But then why would some develop a site that doesn't work like that. For example (with apologies to Brent Rector):

Or this (again, apologies to John Lam):

Shouldn't the 'www' be retired as a relic of the Mosaic days?

Shawn Wildermuth
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