Some of it can, some of it can't... things like cheap table cutlery are stamped out en masse from quite soft metal. Having enough carbon in to make a steel hardenable, would likely make them harder to stamp out and reduce the life of the tools thy use to do it, thus making them more expensive to produce.... no need for a hardenable teaspoon... 
The stainless that can be hardened... and there is quite a lot of it.... needs programable ovens that can go in excess of 1100c and have digital control systems... they are not things you can do at home without the oven...... much different to a carbon steel.
The stainless that can be hardened... and there is quite a lot of it.... needs programable ovens that can go in excess of 1100c and have digital control systems... they are not things you can do at home without the oven...... much different to a carbon steel.
