I wouldn't be surprised if these brands are so dominant because they can afford to flood the country with ads.
coca cola is such a ridiculous product that there isn’t a situation/place/… on the planet where asking for one is odd. you can be in 876 star michelin seven-years-long-wait list restaurant as well as nastiest rats-on-your-should shithole and asking for coke would be the most normal thing
They need to remind you about them even though you already prefer them and know they exist because they want you to buy more than you would otherwise.
I still think a lack of advertising for smaller competitors really would be devastating. DuckDuckGo and Reddit achieved pretty amazing recent growth aided by major outdoor ad campaigns. These were sites that were not market leaders in their categories and had a lot of catching up to do.