I have prospected thousands of booksellers (yes, it's cool, there are thousands of booksellers) over the years, and I have become accustomed to patterns in the responses. Most don't respond, but those who respond in the negative say things like "We are a used bookstore, we don't touch remainders."
Another common negative response is, "We are a rare and antiquarian bookstore, we don’t deal in remainders."
And, "We are a new bookstore, we don't sell remainders."
First of all, technically speaking, most of the books I sell are not remainders, they're returns (see http://benarcherbooks.blogspot.com/p/remainder-bargain-book-overstock.html), but who's counting.
More importantly, the buyers and owners who respond in the positive are, of course, booksellers in some or all of the above categories. They might tell me to restrict my lists to a few subjects or to send a maximum of one list per week, but most of them just say something like "yes, please send me your lists." They then proceed to see what they need and place orders, reorders, and more orders.
My customers are all independent, some owning more than one location, but most only one. They range in size from small to Strand. They tend to be omnivores, buying something from every subject category and even non-book items that somehow end up on my lists. (Have you seen the wonderful puzzles at World…?) They are also inordinately successful, another pattern I've noticed.
I have some truly niche customers, and they too are successful. I do get niche. I've been buying and selling in my niche for around 32 years, so I know niches work. I am sure that many of the prospects who turn me down with are successfully running their niche businesses. I just get the feeling that many of them are leaving money on the table, not to mention customer satisfaction, for an imaginary reason.