• How do advertisements and social media encourage unnecessary spending?

They will implant the imformation of the products in our subconsciousness

When we have the needs (perhaps not very strong), the implanted advertisements will amplify our needs and we will tend to buy it. If we didn't see the ads, we probably wouldn't buy the products.

I think the methods used in consumerism cannot create needs from nothing, they can only amplify them

It seems that these ads create our needs, one point that is emphasized in consumerism.

So seems that these products only provide more ways to satisfy our needs. For example, the car satisfies our needs of more speed, the same as a better horse.