1. Calling some1 by their 1st name in Japan is seen as close friendships. Acquaintances/Non-close friends/Enemies always use the Family name. 2. Military uses Family names all the time no matter where they are. 3. Wesker is a badass name. Albert's just lame.
Why isn't Simmons called Derek? Why isn't Saddler called Ozmond? Why isn't Salazar called Ramon? Because they're villains. and no not ALL villains HAVE to go by their last name. Not everything follows a universal rule. Its just more villainy.
Referring to someone by first name conveys a sense of closeness. NOT the effect you want when the one you're referring to is a bad guy. Just imagine Chris calling Wesker "Albert"....it just doesn't sound right.
The only character I remember calling him Albert is Excella, and she was obviously under the misconception that they were lovers or something.