Because it is open source, all code used to create the program is available to all. Totally different than almost all the software your used to. You wondered who was at the top of the Pyramid? In the code you can see that there is no pyramid, no bitcoin.inc., no official anything. Each of us is the bank, the customer, the payment processor, etc. When you use bitcoin there is no need for a 3rd. party, just the seller and the buyer. The tasks you used to use a bank for are distributed across the network of users.
The security of bitcoin is based on strong encryption. Because this makes bitcoin impossible to profitably counterfeit, there is growing demand for it as a store of wealth. Because it is the fastest, cheapest, and most secure way to pay anyone anywhere; there is growing demand for BTC as a payment system. So, demand is driven by utility.
You answered your own last questions. Why do people use "real" money to buy "made up" bitcoin money? Because all money is just made up. It's just fancy paper that people believe will hold value. And gold is just a shinny rock. Why do you believe in the made up numbers on your credit card?
RodeoX i think you have made the most intellectual comments. Your explanation are very clear and truly demonstrate that you know what you are talking about. Most people who comment just seem to be repetitive but don't have a clue what they are repeating. Knowing something is understanding and been able to explain in your own words.