I think a lot of Americans say this to try to convey that they aren’t some kind of extremist maniac and they don’t want to get in a fight with you over it. Where I live I would be afraid to tell a random person my political views. Yes there are some people who are tuned out because they don’t see themselves as needing to be tuned in. But I do really feel that many people who say this are simply trying to avoid confrontation in an environment where the “wrong answer” to your political views could possibly mean violence