This all reminds me of Pete Rose and the Dowd report. I'm disappointed that lying is common amongst ballplayers and Pete's the rule not the exception.
The consequences of admitting the truth are too great, often. Pete Rose found that out (as well he should have). Remember when everyone was telling him the only chance he had to get into the Hall was to come clean? How did that work out for him?
I have a friend who was involved in a small theft ring (twenty years ago) where he worked. The police called everybody in to a room for questioning and my friend was the only one who was man enough to simply admit what he did.
He was also the only one out of 15 people to get any kind of punishment. He is uninsurable today as an employee for something he did when he was 20.
There is a risk involved with admitting the truth sometimes, including the punishment being more severe than the crime.
My bet is Roger Clemens thinks he's Hall worthy whether he juiced or not, so he isn't going to risk induction by admitting something like this.