Just uploaded a video of me forging a carving knife where I am laminating the high-carbon steel with mild steel and this is an very old way to make tools. Why did blacksmiths use this method? And I am writing "did use" because most of today's tools (knifes, chisels, hammers etc.) is made entirely out of high-carbon steel.
Back in the days during the iron age and until industrialization it took a lot of effort (a lot!) to make iron and it was not easy to get high quality. Iron was a very expensive metal and for tools and weapons a high-carbon steel is also needed which were made from iron but with a few extra steps, so that means it was even more expensive and took great skill to produce good quality.
And that is the main reason why tools were made with this technique by placing the high-carbon steel only where it´s needed to be (the face of the hammer or the edge of cutting tools e.g.) and save some of the more expensive material. But there are other pros with this method too. Cutting tools that is made with this technique will be easier to sharpen since it´s less of the material that is hardened and the sharpening stone will remove material easier and faster compared to a tool that is made all in high-carbon steel. Weapons can be more flexible and durable, lets say a crack appears in a sword and since its made in layers instead of a homogeneous high-carbon steel the crack will stop where the layer stops. In a homogeneous steel the crack will continue and snap the sword.
Forge welding is and old technique and takes some skill to manage, it is also an extra step that takes time and since time is money this extra step is avoided by making it in all high-carbon steel in our modern world.
In my work I use both the traditional and the modern way but I personally like the traditional way better. I like challenges and I still find forge welding a bit magical so I gets happy every time I get the chance to make some sparks in the forge :)