And apparently Hillary did too.
What did she lie about? Comey said she hadn't lied to the FBI. And my understanding from something else I read last night is that Saturday wasn't the first time she'd talked to them. Not to mention the fact that many members of her staff--and no doubt other people who'd engaged in email correspondence with her--had been interviewed extensively.
Martha Stewart was prosecuted for lying to the FBI. Given that, my guess would be they concluded Hillary had not lied to them.
That said, I've always found it's much easier not to lie. That way you don't need to remember what you told to whom.
Ages ago, I read Elena Bonner's memoir of growing up as a member of the Soviet elite back in the 1930s. At one point she said that when she met Solzhenitsyn, she realized he was completely honest. She was stunned, because until then she'd believed everyone lied all the time. She did, and so, she assumed, did everyone else.
I think Trump, and other pathological liars, are like that. They feel it's normal to lie; that it doesn't matter; that probably everybody does it. They do it to protect themselves, to make themselves seem more powerful and important, or even just to make a point. Obviously for Trump, it's only a big deal when somebody else does it.