When you don’t use enough detergent or the detergent is low quality, your clothes won’t be adequately washed, especially if you use lower temperatures. (they aren’t recommended because it won’t destroy some of the bacteria).
Powder detergents don’t lose much of their efficiency over time, but liquid detergents do. That’s why it’s not recommended to buy them in dollar stores. Their business model is to purchase enormous quantities to get the lowest price, and then those products will sit on the shelves for a long time.