Well, Bond's is spending a lot of money too fighting the charges, right? If the penalty is so meaningless why not just plead guilty?
Clearly it's not meaningless to Bonds.
For the government it's about the integrity of the legal system. If people can lie under oath with impunity then the entire legal system might as well be dismantled.
Here's a crazy thought: because he doesn't think he's guilty? I know, I know, cue laugh track.
I don't want to minimize the severity of lying to federal prosecutors: that is certainly a serious charge. But IMO it's important to remember this whole thing started as part of a money-laundering investigation of BALCO, and that Jeff Novitzky was an IRS agent, not some sort of anti-PED guru. Someone leaked the list of players' names to the feds and the public despite the fact that those samples were supposed to be destroyed. There's quite a bit of evidence that the focus on Bonds was due to Novitzky's intense, personal dislike of the guy, and it's at least questionable if the public's best interests are being served by spending a stupendous amount of money on this case.
Bonds testified that he indeed took The Clear and The Cream, but didn't know they were steroids when he took them. That's what the prosecutors are alleging is the lie at the heart of the perjury charges. That's a very, very difficult thing for the feds to prove, particularly as Anderson has told them to go fuck themselves. And Anderson is refusing to testify because the government has reneged on his plea agreement with them.
FWIW, in Giambi's testimony the other day, they read to him his testimony back in '03 that Anderson told him that The Clear and The Cream would provide steroid-like effects without actually being a steroid, and he affirmed those previous statements.