The thing symbolised by hugging is you trust the other person not to stab you in the back.

Handshakes express a lesser degree of trust - holding them at armslength, while mutually checking that there's no weapon in the other person's hand.

As Bill D says up there: "Hugs express something more than a polite handshake". It's when hugs get used in place of a handshake that I distrust them - it's a bit the way you get salesmen calling you by your first name as a technique.