I would argue the reason so many people do that is because every time you visit a Google property it prompts you to do so. Mozilla doesn’t have the advantage of owning sites that are part of people’s daily routines either.

Yeah, but before Chrome people were doing this for Firefox, just from word of mouth.

Word of mouth is quite a bit different. It's the opinion of many unconflicted friends/family vs the opinion of one megacorp with a conflict of interest.