Are you looking to implement win-loss interviews and analysis at your own company? A great resource for insights and best practices is Pragmatic Marketing. The Pragmatic Marketing framework is the de facto standard for training product professionals since 1993. One of the practices encouraged and promoted by the framework is win-loss analysis.
There are various reasons and motives behind the decisions that B2B decision makers make. At Clozd, we have conducted hundreds of post-decision interviews with decision makers across industries. While buyers generally try to represent the interests of their company, many are influenced by one or more of these underlying political, professional, and/or personal motives.
No one is going to tell you your baby is ugly. Likewise, no client is going to tell a product manager that their baby (the product) is ugly or undesirable. Maybe that's a bit extreme, but in practice it's true that clients are hesitant to share critical product feedback with the product's parent. For companies that want candid, honest feedback about their product offering they need to enlist the help of a neutral third-party.