There probably were current legal and Democratic campaign strategy data on the laptops. Keeping them would leave them open to a possibility of FOA requests, leaks, etc.
Excellent observation! The Nixon administration had to sponsor burglars to get data from the Democratic offices in the Watergate building; a corrupt congressional committee could claim access to similarly important data in these laptops under the guise of 'investigation'.
The Fox news treatment suggests that this deal dims that prospect, and the Republican-dominated congressional committee publicly bemoans their lost opportunity. Actually, while the letter from Bob Goodlatte (no other committee members signed it) does include some slanted questions, it is merely a formal request for information. The committee has NOT subpoenaed anything in the computers, and knows no cause ever to do so, and The Honorable Bob Goodlatte has not suggested otherwise.