It's for the end user who purchases a lot of things which include software components to understand the total set of software they're running and be able to ask questions about licensing, vulnerabilities, and establish policies.
A developer (or even administrator of a single computer system) is not the user of something like this, typically.
Here's an example:
A small manufacturing business may have a dozen different machines. Each one has a set of software to control it, running on a computer embedded in the machine. The business also has a website (developed by a contractor), a bunch of software packages purchased from different vendors for accounting, inventory, payroll and scheduling. They probably have some internal home-grown tools too.
1. A new remotely exploitable CVE is announced in a widely-used open source library. Is the company vulnerable to it? Anywhere?
If each one of the pieces of software was delivered with a SBOM along with the actual code, you can use tools like this to look at this globally. It starts to make more sense at the scale of "all the software in the business" is provided by tens to hundreds of different vendors or teams that not only don't communicate with each other but also don't even know that the others exist.