Who said bribery doesn't exist in the U.S. government?

Can someone explain to me the rationale for the government accepting only a monetary settlement from the large financial firms every time they do something wrong? I read today (these seem to be occurring more and more often) that Citigroup will buy back $7 billion (that's BILLION) of auction rate securities from investors and pay $100MM in fines to for their part in marketing this product. However, the kicker is:

"Citigroup neither admitted nor denied wrongdoing under the settlements."

When someone wrongs you, what is more important, that they acknowledge they did something wrong or that they just try to ease the pain of the wrong by paying you money. Clearly being paid money helps to ease the pain but it certainly doesn't make it all right. On the flip side, the government knows that if they fight the case in court, they will pay a lot just to reach a verdict which may or may not be in their favor. The result is that large corporations are being "rewarded" for committing wrongs by only paying a fine but not leaving any mark on their record. I'd like to see how the government would behave if a much smaller firm that couldn't afford the fine or the buyback would be treated if they were simply to admit that they had committed a wrong. I can't recall of such a situation but I suspect that the government would prefer to see the firm go out of business even if they did admit wrongdoing but didn't have the ability to pay such a big fine.

I might be wrong on this and I'd love to hear a differing opinion but it just seems ridiculous that the government spends so much time chasing the bad guys but then never actually achieves anything concrete that will deter firms from committing wrongs in the first place.