Earlier quoted context omitted.
The first thing I do when starting a new project is get everyone on git. If the project is far along and is using svn, I can live with that ... sort of. The next thing I do is explain that I will be spending more time for coding upfront because I will introduce testing into the project. These are not negotiable.
I'd be interested to know how you sell git to your clients. I have listed all the positive benefits of version control in detail to my clients and still have the idea rejected due to it being an "unnecessary complication"...
Other developers can be trickier, but it's very simple to get logical people on the path of version control if you override their changes once or twice. (usually unintentionally)
Actually, the only time I've encountered zero version control, I simply refused to start working until git was introduced into the project.