A couple links here and there don't generate much traffic, but in higher quantities they will. It's a numbers game and it takes years to get good referral traffic unless your site/app/service/product is viral.
Also, not all links are created equally. A link is simply when someone posts out to your site from their own. If they get no traffic, or very little, it's unlikely anyone will come visit you as well.
Link building is just 1 aspect of content promotion that will help you drive traffic (both referral and SEO). And once you find places that send referral traffic, you can intentionally target them to get even more.
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