It is their festival, and they organise it as they, the service people and the veterans like it.

My experience of service people is that they tend not to be religious, but this festival is still popular with them.
They are more tolerant than you Dave.

Jeremy Corbyn is an atheist and is known to be anti-nationalist and anti-jingoist.
He was happy not just to attend in person, but to join in the hymns.

Even among the left wing atheist community our Mudcat ones are unusually intolerant people.