What you call virtue signaling other people call a form of morality. Just because not everyone is doing something doesn't mean that it's not the right thing to do. And even though it doesn't guarantee other countries will follow suit, it's disingenuous to suggest it doesn't make ANY difference. It helps normalize these policies in the global mindspace. Plastic pollution is death by a million cuts. Even though any specific action might be negligible, if we continue piece by piece to remove plastics and encourage investigation and investment into alternatives we can slowly make progress. There are also compounding benefits, if we discover alternatives in one niche it could end up having benefits down the line on other, more significant causes of pollution.