Yes, this site is lazy too, but it _does_ have the marginal excuse of protecting financials, LWN takes credit card payments for its subscriptions and I can see why somebody might not be comfortable authenticating users via an out-of-box third party solution like OpenID in that scenario.
The wiki situation, like web forums, is not like that. The tired excuse is trotted out, "We don't want to inconvenience our users" which ignores the fact that the _only_ reason this doesn't inconvenience ordinary users is because they've learned to type "pa55word" into the box whenever prompted and as a result they have no security anyway (and so MoinMoin contributes to other break-ins all over the web and perhaps beyond). If you don't care about their security why waste their time with the login box at all?
The excuse that it's easier for the developers is stupid, it portrays the situation as "secure password handling is easy, everything else is hard" when in fact the situation is that MoinMoin never really offered secure password handling as we've seen above.