Gatekeeping Advertisers in Publishing?

Reviews are important, vital to authors. No doubt you've heard this many times if you follow authors on social media of any kind. But just how true is that? Sadly, it's very true. 

As an indie author, I get to see just how true. Advertising is a vital part of selling books. Many places an author can advertise that are medium to large sized fish in the sea, require a minimum amount of reviews on Amazon before they will even allow a publisher or indie author to submit to them for advertising. Yep, you read that right, there are gatekeepers even in the advertising field of publishing. 

Even if we put aside hundreds, or thousands of dollars for advertising, we cannot get many of the medium to large advertisers to work with us if our books don't have enough reviews. 50 reviews is often the starting point an author must have on their book before these advertisers will even accept their submissions. There are currently three proven advertisers I'd love to advertise my books with, but I can't. I don't have enough reviews. 

Out of my 6 books published within the last five years, only one of them has enough reviews to qualify, the second closest is only halfway there, and three of them have under five reviews. And, unfortunately, this is after both my publisher and I have done everything we can imagine to try and get people to post reviews on Amazon. We've put the books up on review sites like NetGalley, BookSirens (which give readers FREE ebook copies), and more. I've tried to build a newsletter, and a review team where I have offered free copies in exchange for an honest review on Amazon, but nothing has worked. I am at a soul-crushing loss as to what to do. If you are an author who has found something that works for you, I am open and eager to hear your ideas.