How do you solve your campaign finance system issues if you're not in power because, when you are, all you do is piss people off by banning their cars with little to no heads up?
"Why don't government simply act without any regard for reality?" is just a weird question to ask.
Virtually nobody buys new cars in Denmark because of the taxes anyway, and even if they did, it's a very small country (~5M) and would only account for a very small percentage of global sales. I doubt the subject of Denmark come up in automobile companies' board rooms at all outside of a small footnote on the occasional pie chart.