The banners are not mandated by law. That's an implementation choice. Websites chose to show you annoying banners to make you annoyed with the law. They could just not track you.

Yes, the vast majority of the websites are just being annoying because they are childish. It has nothing to do with the law.

The medium-large company I used to work in the US hired a full-time senior director to address GDPR. He had a team and the effort took years and touched every corner of the company.

The vast majority of websites are obnoxious with consent prompts because they have a clear profit motive that is achieved by harassing and tricking people into giving them permission to abuse their privacy for profit, but I'm sure you know that.

Sob stories about companies being forced to reckon with their unethical business practices in the face of new laws are nothing new. Companies that profit from playing fast and loose with people's personal data complain about the hardships of following GDPR, food companies complain that the limits for cancer-causing chemicals and heavy metals are too low, and factories complain that they should be allowed to dump toxic waste in the rivers.

And employees working for those companies often pick up these sorts of irrational views by osmosis to preserve social cohesion within the company.

I mildly recall them looking to do something about the sort of malicious compliance that cookie banners are, but I haven't been following that work too closely.