Hello, I am happy to help with your question. You've made a great observation about the people in your dreams. I often have to explain the opposite to clients. Dreams are symbolic in nature and so logic doesn't often enter in to the dream storyline or to the characters. The people in your dreams are picture metaphors. The essence of the person is who they are meant to be- as you have figured out already.
It seems that your mind creates more symbolic images than most. For example, when people dream about someone from work that looks exactly like the person, they get confused that it means the exact thing they dreamt will come true. This is rarely, if ever, the case. The person in their dream is a stand-in for some quality they associate with that person. Your mind, simply skips the part about picking a person with whom you can identify a characteristic and goes straight to a symbolic image that represents the characteristic itself! I hope this is making sense.
As far as how you can alter your dreams to include more actual people that you recognize, I'm not sure about the best way to do that. I can tell you that with practice it may be possible to influence your dreams. You can do this by choosing a dream that you have had recently and imagining a different person (or the like-ness of the person whom the dream was about) over and over as you are falling asleep. It may take a few days of practicing this dream storyline before it becomes an actual dream that you have. Another idea is simply to set an intention to have the people in your dreams look like themselves. To do this, as you are falling asleep, say over and over "I will dream about George Clooney (or whomever) tonight and it will look like him...etc". This also may take several nights of practice before the idea shows up in your dreams.
Please let me know if you have questions or details you wish to discuss further. Thank you and good luck!