This is a Quora question I was asked and my answer is as follows.

The only ways I can think of where this happens is as follows:

  1. the existing supplier/vendor is doing a terrible job servicing the retailers and the category buyer is looking for a new vendor to replace them (for example, constant stock-outs, product returns, failure to abide by terms in the vendor agreement, or the vendor does not support the category buyer in any way through co-marketing or maintain the relationship through periodic meetings);
  2. there is an existing supplier/vendor selling to the retailer and it benefits both sides to add the product on shelf (for example, it is incremental sales to the vendor, and the retailer has one less vendor to deal with);
  3. the category buyer does not already sell such products and can benefit from adding them to their assortment, but given it is a product with no differentiation, then it usually comes down to selecting the vendor with the best pricing/terms to the retailer and/or one who does the most outside marketing to support movement of their product versus the competition.