Cookies don't track you nearly as well. What happens if you delete a cookie? Fingerprinting isn't a universal solution either as iDevices all look extremely similar to each other. As to IP addresses, they only work if you connect from your home WiFi. Not every phone has that set up. Often they use carrier grade NAT so you only have a few IPs to work with.

Last, customers of their data love being able to search/correlate by phone number, not by some pseudonymous identifier that might not be present in some other dataset.

I think this crackdown might in fact be a reaction to attempts by institutions like Apple to ensure better privacy. If fingerprinting isn't giving them the data, they ask for it directly at the threat of restricting access.