{0} other people being immature has no bearing on the strength of your argument.
{7} They use flash carts on the DS, how does using flash not make sense? You can reach a much larger market selling physical medium than you can online. Online only has a long way to go for the larger market. Online only can be successful, but it doesn't have the same reach.
{9} All 3 companies outsource their manufacturing to the same exact hardware manufacturer (foxconn). Nintendo started with cheap parts, which tend not to drop in value, while Microsoft and Sony started with expensive parts, which do tend to drop in value.
{1/11/12} Nintendo has already stated, that if they leave the hardware business their software will die with them. Nintendo will take risks until they go out of business, so the size of the market doesn't matter.