@Logicfest -- yes, companies do raise money by selling stock to shareholders, but a shareholder loan is a completely different breed of cat for a couple of reasons.
First of all, a different relationship is created. A shareholder owns a piece of the company, but a shareholder loan is held by someone who is considered a creditor. Without mincing through the legal details, an owner has different rights and obligations than a creditor does.
Second, the shareholder loan is a loan in the truest sense of the word -- you've got a lender with a loan secured by something of value (shares of stock, property, etc.) The term shareholder loan can be a bit misleading because it suggests that the "shareholder creditor" is somehow different than a "regular creditor." There's really not much difference outside of the fact a shareholder is more vested in the profitability of the company than a regular lender is.
Finally, a shareholder loan is typically issued for a specific program, while shares of stock are issued for more general purposes. A private company goes public and issues stock when it wants to raise capital to expand in various ways, whereas a shareholder loan is taken out by a a company that already has shareholders and needs more capital for very focused, short-term reasons.