The reason CA's do this kind of stuff is because no one makes complaints against them, because they are afraid. That is why if you look up some of these 'bad' companies everyone is complaining about, you will find that the BBB says they have satisfactory record. People think that because they owe the money, that making any complaints against them will result in retaliation that they cannot afford.
Another reason I think, and this is just my opinion, is the type of people that a lot of (not all) collectors are...they are in it for the money and have no regard for other human beings and their problems. If these collectors were not working primarily on commission, these problems would not occur...but on the flip-side, if they were not working on commission, the companies they collect for know they would not try as hard to collect the debt, which I am sure is true.