Why do I need to bid on keyword ads for Amazon if I’m the only one with my unique Brand Name???

I realize people may not find my product as fast as if I had run the ads…. but I’m not really in a rush anyways. I’m studying this ad stuff and it looks like if I put a higher bid on a keyword then Amazon is at least “supposed to” have a greater chance of letting my ad be shown??? I cant move too fast with my business anyways so why don’t I just let it grow organically and by word of mouth??? I’d say if a product can pass that test without this “keyword bid” stuff then thats nearly a sure fire sign that you’re selling a product that’s already likely to be a success anyways….. I mean, am I reading something wrong here?… because I don’t think I am…

Maybe you can help me understand, thanks