It's really better that way. Real real people simply aren't up to the task of appearing on camera. Nine times out of ten they'll be too nervous, too regional, or too wooden. The bottom line is that they can't be real on cue. And most often, that means that real real people are just not believable.
Professional actors fare much better.
They can do endless re-takes without losing freshness, they stand where you tell them to stand, and when they smile, they don't show a crying need for emergency dental surgery. Let's hear it for Central Casting Probably the best reason to use actors is that you can choose actors. You can cast the ones who really look the part. And casting is very, very important. That's why they hire actors to play all the real people who are Italian mamas, teenagers, airline pilots, cheerful phone operators and cool-hand cowboys.