My answer is that when confronted with the obvious, the most common human reaction is to seek reasons for it, because things have to be right. They have to have a reason. We don't like it when things suck.
So when finding out that you are being ripped off every day of your life, your reaction is "There must be a logical reason that perfectly explain why this is. After all, the world is fair, governments are working in our best interest and if they do it this way, they must have a very good reason for it."
Sorry, but that not the case. You have the facts. You are just not looking at them.
Economics, as a subject, is the proper management of resources and production. Now, forget the fancy theories, the elaborate nonsense about stocks and bonds and currencies and pay attention to the actual situation.
On our planet, most people earn $2,000 per year. Clean water is not available for a very sizable percent of the world's population. Admittedly, 90% of the world's wealth is concentrated in the hands of the most wealthy 10%. A Chinese engineer earns a fraction of what a similarly qualified engineer earns in the States. Most people, even in rich countries, have a negative net value. They have mortgages that run for a third of their lifetimes, credit card debts, loans... do the balance. Most people are broke.
Does this strike you as the logical result of a fair and balanced economic system?
Does this look like a random happenstance?
The dominant theory is "It just happened, it's nobody's fault and nobody designed it that way and to think otherwise is very bad because it makes you a conspiracy theorist, and conspiracy theorists are nuts. You are not nuts are you?"
Look at the facts already in your possession. It didn't just happen.
The system is rigged. When a suit typing a few numbers in a computer can make more money in 5 minutes than an average Joe can make in 100 lifetimes of honest, productive work, you don't have a fair economic system, you have a scam machine.
When you look at a system as broken as the one we have, you shouldn't be asking yourself "what makes this system right?" What you should be asking yourself is more along the lines of "Why is it broken? Who benefits? Why did congress turn its monetary policy over to the Federal reserve (a group of unelected and unaccountable individuals with strong ties in the banking industry) and does not even bother to conduct audits to know how your money is actually managed?
This brilliant movie, Money as debt, points to a number of outrageous bugs in our economic system. Now, you can dream up reasons why the system should be the way it is and why it is an acceptable system. Or you can look at the fact and realize that there is NO JUSTIFICATION for an economic system that perform as badly as it does.
Back to basics. Money is supposed to represent production. It's in every basic textbook on the subject of economics. So, what should money creation be based on? Debt? No. Gold? No. Randomly printed by the government when they feel like it? No (although this could actually be better than the 2 previous suggestions)
Money is supposed to represent production. Index money on production and you have a sound system. Why isn't it done that way? Why do you think that is?