Why does the AP insist on calling Joe the Plumber Samuel Wurzelbacher?

Compare the AP’s lede paragraphs

“Joe the Plumber” says adding taxes on services – like plumbing, perhaps – isn’t the way to go in North Carolina.

Samuel Wurzelbacher, who became a hero to some Republicans during the presidential campaign when he challenged Barack Obama on taxes, said Wednesday at a conservative rally that a tax on more services – such as those proposed by some General Assembly members – would only get passed on to consumers.

With the News & Observer’s description of Joe

A collection of conservative groups brought in nationally recognized speakers such as FOX News’ Mary Katharine Ham and Joe “The Plumber” Wurzelbacher to speak against proposed tax increases in next year’s budget.

Wurzelbacher, whose questioning of Barack Obama’s tax policies in the 2008 campaign brought him prominence, urged people to get involved in politics and hold government officials accountable. “This is our fault because we vote these guys in and then go about our business,” he said.