When you have the "next Facebook idea" there is no off-the-shelf software you can use or adapt. When you want to be original and unparalleled in your product, you'll want to do it from scratch. There are great advantages in having a custom made software. It would meet all specific requirements, making your business run smoother unencumbered by restrictions given by existing systems.
We don't exactly reinvent the wheel ... that wouldn't be cost effective for our clients (we do that on our own time, developing in-house wonders and projects, but that-s another story). But we do find new ways to use the wheels.
We have experienced developers and software engineers that can understand and put down your basic ideas comprehensively. And using the existing programming languages and tools, they will create for you wonderful frameworks and tools that will boost your business.