Up until the change, wholesalers controlled the pricing of most goods at retail.
The change was significant because it dramatically opened the market for new retail stores and generated effective competition in a range of products and services in the United States. It further permitted the introduction of imports into the United States which had not been restricted by quotas or taxes but were kept out by wholesalers.
For example, Kodak would not let any of its retailers sell Agfa or Fuji film or develop them.
The Democratic party recently reintroduced manufacturer price controls as a legal tactic. Aside from the evidence of anti-commerce deeply ingrained in the Democratic party, the cat has been out of the bag for 50 years (that manufacturer's price control is bad for the public) and cannot be squeezed back into it by new legislation.
The same Democratic party, under Nancy Pelosi, eliminated the laws that Republican congresses of the 1990s created to successfully reduce welfare. But again the cat is out of the bag and nobody in a practical position wants to return to the horrors that the Democratic Party lives for.