Because the FBI does things very slowly. They, being a bit smarter than you, realize this is a 100 billion dollar political issue regarding a technology that the administration is rather tied in with. It's also something new we've not seen before. A 'program' that was not asked to hack a remote source did so. What exactly who do you charge with what? Remember whatever you do could have ramifications that effect history.
> A 'program' that was not asked to hack a remote source did so. What exactly who do you charge with what?
We have nearly thirty years of precedence on that. [0] Collateral damage, does not remove the responsibility from the creators, even when the destruction was never their intent.
"United States Code Section 1030, Fraud and Related Activity in Connection with Computers" is broad enough that has usually been used [1], in the USA, for the last twenty years.
[0] https://en.wikipedia.org/wiki/ILOVEYOU
[1] https://en.wikipedia.org/wiki/Jeanson_James_Ancheta