Here comes the philosopher.
I think that part of Wayne's ability to get into character is part of why we read books: To escape from our present reality and go to a different one where we don't have to deal with hard things. Of course, the illusion always ends, we put the book away, but face our struggles a bit better, knowing we can run from them at any time, but we don't, because we would be going against what Vin, Kelsier, and others do/did when things get rough.
And that is why Wayne mimics people.