Not everyone’s lucky enough to keep all their gear where they work. Some people have the personal gear they talk to at a workshop, a school, etc. Why you’d need a welding bag specifically, rather than just a normal bag – well, you don’t, strictly speaking. There are plenty of bags that can store your gear. But welding bags are designed with the needs of welding gear specifically in mind. Welding helmets are awkwardly shaped and large, and your welding bag is designed to take this into account. You could shove everything into a regular duffel bag – but you might as well get something designed for the task for the best results.