There is no difference, the not-invented-here build-my-own is just as common for software developers. For example, do a search and tell me how many different XML/HTML parsing libraries you can find. Then look on stack overflow and see how many questions you see people asking about how to parse HTML with a fricken regex.
There are lots of tools for building chroot environments. For example on a Debian-based system I would use Debootstrap, but there are many other similar tools. But there is no perfect tool that works for every distro, and every person. Plus people look at these tools that try to be generic, and find that they are more complex, which they have to be to provide the required flexibility for a generic tool. So they decide to build their rather then spend time learning.