Best Practices for Cookie Notices
web.dev
web.dev
That's why any bigger website will have a huge popup that will require you to consent before doing anything else - they need you to consent and then they enable trackers.
Smaller websites just don't care and put a small cookie notice banner stick to the bottom, and enable GA anyway. Most users probably won't even bother to click it, as it's not disruptive. It's therefore not GDPR compliant.