And your own computers require expertise so expensive and frightening that no sane company would host their own computers.
How Amazon created this alternate reality should be studied in business schools for the next 50 years. Amazon made the IT industry doubt its own technical capabilities so much that the entire industry essential gave up on the idea that it can run computer systems, and instead bought into the fabulously complex and expensive and technically challenging cloud systems, whilst still believing they were doing the simplest and cheapest thing.