Here is a basic answer to your questions:
because monopolization(sp?) is illegal, and having 1 system that plays everything is just that, a monopolization(sp?) of the gaming industry, which would mean the company that holds the rights to the said system could charge what ever they wanted, because your only choice is them or nothing. imagine paying thousands of dollars just for one game. then youd be wishing for multiple systems.
Which is why there's competition. =P
because monopolization(sp?) is illegal, and having 1 system that plays everything is just that, a monopolization(sp?) of the gaming industry, which would mean the company that holds the rights to the said system could charge what ever they wanted, because your only choice is them or nothing. imagine paying thousands of dollars just for one game. then youd be wishing for multiple systems.