If those companies had to rely on me buying products from those companies multiplied by tens of millions of people, 90% of those companies wouldn't exist that you mentioned
So you don't buy Microsoft or Apple products? What computer do you use then and which operating system?
Your opinion is irrelevant for the mass behavior of people who do buy all these products. The fact that these companies exist proofs that they have billions of clients.
Amazon has (estimated) 300 million clients, Apple has 800 million.
I even forget in previous posting: Facebook, Snapchat, Whatsapp, Twitter...