Many don't do this because they don't feel the need. I've spent about a decade in the US as a green card holder, and the only cases I ever been asked for it is either crossing the border or being hired. And I never heard about anyone being fined (let alone going to prison) for failure to carry the green card on them. Yes, the law says that, but I don't think anybody paid much attention to that, at least until now.
Immigration law enforcement is at the discretion of the Executive (President). If the President decides they want to pump up the numbers of deported criminals, doing anything that's technically a crime as an immigrant is a risky proposition. Even saying you do it on a public forum is risky.
You act as if the last 6 months are a continuation of the the last 9.5 years, and there is some status quo that hasn't changed. Maybe for an affluent SWE in his Tesla, but this isn't the case for many on their way to work in a construction work van.