Why does NASA need multiple websites for the same mission?

The following is put at the bottom of most press releases issued regarding Mars Curiosity. Why does NASA pay to maintain three separate websites (two run by JPL) – all of which are out of synch with one another?

“More information about Curiosity is online at: http://www.jpl.nasa.gov/msl , http://www.nasa.gov/msl and http://mars.jpl.nasa.gov/msl.”

NASA is constantly complaining that they never have enough money to run all of their EPO and PAO operations. Yet they can afford multiple websites when only one is needed? If you ask NASA about this (it happens with virtuallky every mission), you either get no answer, a shrug and/or sigh, or something really stupid. So, I am asking (again) …

– NASA’s Tangled Human Spaceflight Web Presence, earlier post
– NASA’s Sprawling Web Presence, earlier post
– NASA’s Inability To Speak With One Voice Online, earlier post