using a screwdriver as a chisel

They're simply designed different due to having different uses. Screwdrivers are designed to turn, and chisels for blunt impact. Better chisels usually have a full length shaft with a full strike on the end, and the handles are usually considerably larger than screwdriver handles, no doubt to give most people a better chance of hitting the strike instead of their hand ; ) The strike isn't hardened as much as the point so not to throw sparks when hit with a hammer, but glasses are still mandatory if you appreciate your eyesight. Cold chisels are tempered the same way (hardened point, softer strike) and are intended to be used with both glasses and gloves