It seems to me that Al needed Sam to "anchor" himself at a certain point in time.
Right, and the only reason Sam and Al were connected was because they both donated neural tissues to the creation of Ziggy, so they were linked through her. They did eventually find a way to link other people to Sam as holograms, and clearly the new team has found another way to do it, but it's not something you can do without an actual time traveler to link to, apparently.
Now, intelligence gathering aside, why didn't Al use some free time trying to see what had happened in unsolved crimes instead of peeking into the ladies' dressing rooms? I think I remember that there were times when Sam stayed weeks in the past. If Al used a couple of hours for the common good it wouldn't be bad.
Again, it would depend on being coincidentally at the right time. Also, if the program is classified and time travel is not provably real, how would any such information stand up in court?
Although I think there were a number of cases where Sam's mission was to clear an innocent person's name or ensure that the real criminal was caught.