But lots of things that are 'ordinary' - going to work for example - have people wearing smarter clothes than the ones they mooch about in on a lazy weekend day in the garden.
Some people change into leggings and PJs as soon as they get home and practically live in them. Doesn't mean they go shopping, to work, to the pub, to the school run etc in PJs.
And yes, I am aware some people do - but it's quite normal to change your clothes to suit different occasions.
Remember this is all in response to the posters who have said why don't the royals wear their normal clothes to church - and I'm pointing out that for many of us smart clothes are our normal clothes when out and about interacting with other people.
The hats are just tradition for them. But the rest of what they are wearing looks very normal to me. In other words - it's not a performance for them just as it wouldn't be a performance for me.