Maybe the seller want's to private his personality. Its good for you both to hire a trusted escrow just to make sure you're money will not lose. But I see no reason why the seller doesn't wan't to show up his face it turns me up to curiosity.
You somewhat answered your own question. If we dig a bit deeper into why people wouldn't want to deal with random people, then it's safe to say that it's done to maintain a non crypto profile for the outside world. I would trade in this exact same fashion as well. In fact, I have sold coins through a proxy to someone who was in need of Bitcoin that wanted to pay a fair premium. The main point is that as long as the escrow (ie, proxy) is a reputable party that both the buyer and seller agree with, it's not a problem at all. In this case the escrow could even test if everything works properly.
Yeah. I'd never do a face to face, especially as a seller. There's nothing wrong with wanting to keep as much of your privacy as possible - in fact, there's everything right with that. Not to mention personal security. We're talking about a lot of money and very specific, very expensive equipment here. I'm pretty laid back when it comes to my physical identity in relation to crypto, but then I'm not dealing with this kind of financial and monetary risks...
As pointed out rather creatively a few posts above, (a solid) escrow is really all you need. Protects both parties' interests and ensures both sides get what they want without much fuss.