Because, after The Clinton administration imposed it's draconian "purity" rules with regard to human intelligence, it was the only pipeline left open. Thanks to Dems gutting the ability of our intelligence agencies to gather human intelligence, this is what we are left with. Rather than blame the agencies for trying to do their jobs, blame the people that tied their hands.
Reliable human intelligence sources take years to cultivate and require trust. Since the days of the Church commission, our intelligence agencies have had a difficult time of things. Spies don't want to be left spinning in breeze with every change of administration and foreign policy. Lack of funding and inconsistent policies from one administration to another have left us vulnerable in this arena.
We are now left to buy "information" from whoever wishes to come to us with it, provided they squeeky-clean, with little ability to vet sources and corroborate the intel.
The fault does not lie with our intell agencies. It lies with the politicians.