According to his former mentor, the answer is more prosaic: Morgan is too shy to sing on camera.
Invited during a press conference in New Zealand to discuss his reasons, Morgan said it was "a long story" and "a personal thing", adding that he wouldn't sing the Irish anthem either.
He would not elaborate, saying only: "It's pretty simple. I have never sang the national anthem when playing for Ireland or England. It does not make me any less proud to be an English cricketer.
"I am extremely proud to be in the position that I am in and privileged to be captain of the World Cup side."
Kevin Jennings, the deputy headmaster who offered 11-year-old Morgan a scholarship to Dublin's Catholic University School and guided him through his school years, said his former charge was not political at all.
"He's a very shy fellow. I would imagine he'd be quite self-conscious singing in that context. I would say it's as simple as that. He certainly wasn't in the school choir," said Mr Jennings, now retired, a friend of the Morgan family.
"I've known him since he was 11 and he was always very quiet and reserved. Where he was confident was going out to bat.
"I know people could read something into it, but I don't think it's political. He certainly isn't political to my knowledge."
Mr Jennings said Morgan was always "well-mannered and polite but never an extroverted fellow. He wouldn't overdo the chat. When I see him do these press conferences now I think, he couldn't have done that seven or eight years ago. He must be coached for that."
Anthems are rarely played at cricket matches; in England, Jerusalem is played instead, with rare exceptions made such as the first morning of the first Ashes Test.
The sight of him keeping his mouth firmly shut during the anthem earlier this week angered some England fans, including Piers Morgan. But others, Gary Lineker among them, jumped to his defence.
Those leaping to Morgan's defence included Gary Lineker, who replied: "Not everyone is comfortable singing. Some do, some don't. Doesn't alter performance. I used to hate singing it. Still do. Mainly because I'm hideously bad. Don't understand why it's important."
Morgan, 28, was born and raised in Rush, County Dublin, honing his skills on a concrete strip bordering his housing estate. Cricket is not one of Ireland's more popular sports but has a long history in the area north of Dublin, where estate landlords would play their tenants in regular matches. Morgan's father, grandfather and great-grandfather were local players.
"There's no reason Irish guys won't want to play for England," Morgan has said. "You ask the Irish captain at the moment if he wants to play for England in Test matches."
He is the third Irishman to captain England.
Morgan was appointed one-day captain in December, replacing Alastair Cook. He was thrust into the spotlight almost immediately when he was targeted in a £35,000 blackmail plot.
The England Cricket Board received an email threatening to share "sexual" messages Morgan had sent to a girlfriend, Brooke Tsakirakis, when the couple dated five years ago.
The ECB contacted the police and the emails were traced back to Miss Tsakirakis's current boyfriend.
Morgan, who is now in a relationship with law student Tara Ridgeway, maintained that the episode had not been distracting.
His reluctance to sing the national anthem is in stark contrast to the attitude of Harry Westlake, the six-year-old mascot for the England rugby team at Twickenham.
Harry became an online sensation when he belted out God Save The Queen before England's game with Italy, prompting England's Mike Brown to call him a "legend".
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