In general this is true, there are always reasons for bad practices but what if the some teams in the company don't use a source control system, they just use f

In general this is true, there are always reasons for bad practices but what if the some teams in the company don't use a source control system, they just use folders on a network drive? If I came in to manage such a team. I would absolutely say so in no uncertain terms. I have actually been in a similar situation but I did have the backing of senior management, in fact that was the main reason they hired me. They wanted somebody with experience in the industry to drive best practices so that they could show investors in order to attract investment (they had had two investors pull out after some due diligence showed that from a technical POV the company was in dire straits)