It's generally quicker and cheaper to go that route. Incorporating and issuing your own shares subjects you to filing with the state and/or SEC (which can take months and a lot of waiting), and forces you to comply with the countless securities laws and regulations that pertain to the sale of securities. Then you would have to apply for quotation (another long process usually) before you can begin trading, etc, etc etc. There are other reasons, of course. But that's a good start...
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