Before the advent of products liability, persons injured by defective or dangerous produces were forced to rely on traditional tort (usually negligence) claims to be compensated. Those type of claims worked in an era when everyone knew with whom they were interacting. For instance, the person who bought bread bought it from the individual who baked it, not a downstream retailer that purchased the food in bulk.
Traditional tort theories were inadequate to address the injuries sustained by people in the modern world. The advent of modern consumerism at the end of the 19th Century introduced a new type of injury: negligently designed and manufactured products. For the first few decades, persons injured by defective and dangerous products were usually incapable of holding manufacturers accountable. To win their cases, injured persons needed to gather substantial proof to establish that their injuries were caused by a particular negligent action on the part of the defendant.
Modern supply chains may involve many companies. The injured person may be unable to prove when the defect was caused. The injured perseon could clearly suffer an injury, and the product could clearly be defective, but without specific causation, there could be no recovery.
Into this gap, the courts (and eventually legislatures) designed products liability. Products liability is a "strict" tort. Strict liability means that the plaintiff does not need to prove specific causation, the plaintiff need only demonstrate that they suffered an injury due to a defective product. Once that is accomplished, the plaintiff can recover from any of the companies in the supply chain. The burden is then on the companies to prove which one of them is guilty of the defect, in order to sue for reimbursement from the underlying lawsuit.
As you can tell, products liability suits are not nearly as complex as they once were. But, proving that a product is defective has become much more complicated. If you were injured by a dangerous product, you might want to contact a lawyer for assistance. Investigating the manufacturing and design process of a company is complicated and full of legal loopholes. You will want the help of a lawyer to navigate these issues.