What is the main benefit of Repository<T> in this example?

interface Repository<T> {
  findById(id: string): T | null;
  save(entity: T): void;
}

type Product = { id: string; price: number };

const repo: Repository<Product> = {
  findById: id => ({ id, price: 10 }),
  save: entity => {
    console.log(entity.price);
  },
};