I recently worked for a company that had a single environment, yes, even development was done against production databases. I worked there for awhile and at first, I was aghast at how weird it was. Then when I left and went back to multiple environments; I am again aghast at how complex it is -- not to mention that there isn't much 'force' to push you to learn how to recover from mistakes in production (leading to more downtime than I ever saw with one environment).I was curious about when multiple environments became 'standard', but it appears to be a thing for as long as the internet can remember. Can someone who has been writing software since before the internet remember why we started to do things this way?