Why do some stores have signs stating that peers are not allowed to enter?

This is to prevent peers from entering the store to check their own products and product prices. Or store layout, etc. As the saying goes: peers are enemies. If they know it, the other party can change their business methods, so no peers will be allowed in. Because you know yourself and the enemy, you can be victorious in every battle. Only when your opponent doesn't know the bottom line can you stand firm.