Technical Writing: Product Information.
Technical writing bridges technology to the people that use it. The function of a techical writer is, with clarity and economy, to let users understand how a piece of technology works and how to use it to suit their purposes. It can be stated that, by definition, anything devised by mankind involves some level of technology.
Technical writing, therefore, is required in some form for businesses to show customers how to use their products and services, as all products and services involve technology and methodology to some degree. It's customary: unless its use is entirely intuitive, a product or service must also include guidance in how to use it. This fact is obvious in that in any item sold in a store or online will have information about its assembly/use/maintenance either printed on its label or container or on an accompanying sheet or document.
As a technical writer/illustrator with over two decades of experience, I've produced product information for employers and clients ranging from large corporations to small startup businesses. My background as both a writer and an illustrator has been useful: I can convey the necessary information about a product using either words or images or both, whichever will be the most effective. ( 'One picture is worth 1000 words.' can often be true.)