Is royal military service becoming a waste of time and money?

A recent article by the Independent is calling Prince William's newest attachment to the Royal Navy "the latest development in a PR initiative that befits a new generation of princes," which got me thinking - with all the money invested in training soldiers, sailors and airmen, is it really necessary to (unofficially) require members of Royal families to participate in the military?

The Imperial Age has ended. Wars are waged by diplomats and the press, not by Kings on horseback. While Alexander the Great certainly benefited from military training, what exactly do modern royals get out of it?

Take a look at Prince William, for instance. Tomorrow morning, he will begin training with the Royal Navy- he will train for about 3 weeks and then spend another 5 weeks on a frigate in the Caribbean (that's a type of ship, for us civilians). The mission is to attempt to stop drug smugglers and provide aid where needed. Considering that this sort of training normally takes 2 years, will one more completely inexperienced hand on deck make a difference in the overall effort?

I don't mean to beat a dead horse (I swear!), but in looking at this from the perspective of a tax payer, is it worth spending tens of thousands of pounds training someone who will be virtually useless? Or in the worst case scenario, not only worthless but also wasteful, by taking (for example) a military aircraft to a stag party perhaps?

Is this 'new generation' of royalty not fulfilling the expectations of the past? Taking a look at an older generation of royals in the same position as Prince William, one can see that military training is taken seriously elsewhere. One must ask, why is Prince William not putting forth the same amount of effort as his elder counterparts in Spain and Denmark?

His Royal Highness the Prince of Asturias

• Military training: General Military Academy in Zaragoza, the Naval School in Marin and the General Academy of the Air Force in San Javier from September 1985 to July 1988. He then attended a refresher course in Security and Defense from September 1999 to June 2000.
• Ranks held: Commander of the General Land Army Corps (Infantry), Lieutenant Commander in the General Navy and Commander of the General Air Force. He has his Helicopter Pilot's Wings for both the Land Army and the Navy.

Crown Prince Frederik of Denmark

• Military training: He began as a recruit in the Royal Life Guards in 1986; Lieutenant of the Reserve 1988; Platoon Leader of the Household Troops 1988; First Lieutenant of the Reserve 1989; Danish "Frogman" Corps in 1995 (equivalent of the UK’s Special Boat Squadron or the US Navy SEALS); First Lieutenant of the Naval Reserve 1995; Lieutenant Commander of the Navy 1997; Captain of the Army Reserve, 1997; Captain of the Air Force 2000. Studies at the Defense Academy 2001-2002.
• Ranks held: Major of the Army and Air Force Reserve and Commander in the Navy.

Prince William does not have the same passion for the armed forces that his brother does. Why then, is he being forced to serve? Wouldn't his time be better spent in humanitarian efforts that interest him? Perhaps the problem lies not in his disinterest in the military, but in his disinterest in all his royal duties? Perhaps his family pushed military service on him simply because they were afraid he would idle his time away otherwise?

Or, perhaps he's simply a lover and not a fighter. I suppose stranger things have happened.