The way I looked at it if you’re not doing anything wrong, why wouldn’t you carry ID?
If you’re not doing anything wrong, then why should you be obliged to do anything?
Not trying to trample your rights here, just giving my experiences of living in a country that required people to carry ID. I found there was no downside to it, and occasional upsides – that being on the few occasions when I needed to prove who I was, it was achieved simply, quickly, and without any embarrassment, and I was on my way again.
There is another argument for carring ID of course, and that is that the law abiding majority has their ‘rights’ marginally infringed by having to carry identification, in order that the police and other officials we employ to enforce our rules and keep us safe can do their job more effectively. We make these compromises of personal freedom in the general interests of society more readily in other aspects of life – having number plates on our cars for example, but carrying personal ID seems to generate much more emotion!