Why not since it's their birth name.
No. The question is: "why would you?" Since nobody uses those names, including their own family and they themselves.
But of course, you've already said in the past that somehow YOU feel it's important to acknowledge his Greek heritage. Yet, again, he nor his family it is important to do so IN THIS WAY.
But we all know that in reality, you feel that it is insulting to Sampras to use this name (which is really quite an ugly prejudice on your part), and you get off on doing this and being a contrarian. That is simply sad.