Why would anyone want to stop this when there's so much political mileage to be gained from it?
The longer this goes on, the less credibility everyone involved with it has. That's why Trump and Sessions have taken a hand's off approach to the whole affair. This is purely the democrats' doing. They're the only ones running the show. Trump knows they can't find anything so he's giving them all the rope they need to hang themselves.
Sessions has taken a hands off approach to his job period. Why did he let Lois Lerner off the hook? Clapper? the Awans? Jeff is working for the other team, plain and simple.