It can guide policy decisions (e.g. "Is it more important to subsidize/mandate sustainable meat production or phase it out all together?"), can make voters think differently about topics, which in turn influences politics (in democracies) and can be a simple way to put into perspective the impact of millionaires and billionaires compared to average people.

Also I've heard people justify flying a lot because the "carbon footprint" is made up by the fossil fuel industry, which in my eyes is the same argument as "My country only makes up X% of greenhouse emissions so we shouldn't implement a carbon tax/invest in renewable energy/... until China/the US do".