So ... you're anti-Cameron, eh? Now, who's being biased?
Well ... does he really need a reason? ... apart from the MAIN - and, I would say, ALL IMPORTANT - fact that, as Prime Minister, he's Head of HM Government and, as such, it's naturally enough expected of him.
There again ... ... like countless others, he too, may have lost a grandparent (or great-grandparent) amidst all the horror and carnage of warfare in the 'Trenches'.
At least - unlike his opposite number - he had the good grace to actually personalise his tribute to the fallen!