It's a good thing practice and theory are two different things. If practice had to conform to theory, capitalism never would have gotten off the ground. Economic theory has been positively criminally negligent in its lack of capacity to deal with the realities of capitalist practice. This is because from classical economics onward, economics has restricted its purview to the exchange of goods and services -- the so-called real or natural economy -- neglecting the fact that, as Henry Dunning Macleod pointed out over 150 years ago, the greater portion of what is marketed is not goods and services per se but debts, claims on goods and services, to which John Rogers Commons (following Eugen von Böhm-Bawerk, himself a skeptic in these matters) added a third category, intangible property, i.e., goodwill, which makes up a good portion of what one buys when one buys shares on the stock market. These are all marketable assets, but to make them into goods and services is to beg the question of what a good or a service is.
So economists have neglected these other categories, considering them to be mere derivatives of the primary category of goods and services, and therefore safely ignorable. There have been exceptions -- the above-mentioned Macleod and Commons, for example. Macleod is quite interesting reading, and even if his exposition on banking and currency does not quite go far enough, it does go quite far in capturing the reality of capitalism for the benefit of economic science (for those with ears to hear, of course). Commons can be virtually unreadable, and his anti-capitalist bias is constantly undermining his analysis. Still, there is much to learn from him as well. Irving Fisher is another economist who recognized in business practice, and particularly in accounting practice, that there is more to economics than exchange of goods and services. Still, his quantity theory of money betrays little influence of that recognition. Ludwig von Mises as well recognized the importance of business practice, especially with his recognition of the importance of capital accounting. But once again, this had no impact on his view of credit expansion and currency, which, as far as I can see, he analyzed purely within the paradigm of commodity exchange.
Recently there has arisen a new form of economics that has successfully integrated the realities of capitalism into economic theory, by discovering the basis of interest, the sine qua non of comprehensive economic science. Unfortunately for English-language readers, the language in which this economics is exposited is German. The exponents are Gunnar Heinsohn, Otto Steiger, and Hans-Joachim Stadermann; the key text is Eigentum, Zins und Geld: Ungelöste Rätsel der Wirtschaftswissenschaft [Property, Interest and Money: Unsolved Mysteries of Economic Science] (4th edition 2006), by Heinsohn and Steiger, along with Allgemeine Theorie der Wirtschaft. Erster Band: Schulökonomik [General Theory of Economics. Volume 1: Schools of Economics] (2001). For the longest time, a translation of Eigentum, Zins und Geld has been "forthcoming" from Routledge, but there is still no sign of it. It really is an example of the guild mentality of economists that such a book still has yet to be translated! The same holds true for the General Theory, Vol. 1, which contains trenchant critiques of classical economics, Marxist economics, neo-classical economics, and Keynesian economics (as does Eigentum, Zins und Geld for that matter, although not as systematically). Once again, I will blow my own horn. I have included a summary of the importance of this school of economic thought in the chapter on "Common Law Economics" in my book Common Law Conservatism. So, if you are interested in this subject, don't neglect my little book!