I think it's because they don't want to be in the position of making an offer to someone they explicitly rejected when the preferred candidate didn't work out.
Hmm, in my case at least with a bunch of companies, they had laid out the interview process (say, 3 or 4 steps) and they stopped communicating after the 2nd or 3rd step (with more to come) so I don't think they had me as a secondary alternative, I don't know why they can't just say "Sorry, you are not the right fit for us" and _then_ stop communicating for the legal / time waste reasons the article gives.
