The number of houses that can be searched is limited.
Actual police officers or detectives need to visit said house, spend time on-prem, collect, and analyze evidence. A single site can be accessed at a time.
Digital media are searched automatically, by hardware and processes, with many potential targets searched simultaneously and at vanishingly small cost.
Physical evidence and print media are far slower to access and assess than digital media are.
Physical evidence and print media have vastly lower data density than digital media do. Both temporal and spatial data resolution is far lower for the former. At the same time, provenance, integrity, and chain-of-possession over physical evidence media are also generally easier to ensure and assess, and both are generally less susceptible to either fabrication or modification.
(The point here isn't that physical media cannot be tampered with. It's that digital media can be tampered with absolutely no evidence of this on the media itself. Typically some external validation or integrity check is necessary. Digital media can be entirely fabricated, all the more so now with AI and generator technologies, or can be entirely destroyed without a trace.)
Digital media can be stored at volumes and for durations which would be utterly impossible with physical evidence.
A 1 TB storage device, which can fit on your pinkie nail, can hold the equivalent of ~200,000 books, roughly the size of a fairly substantial public library. The entire Library of Congress book collection, 140 million volumes, assuming 5 MB each, would fit in 700 TB of storage. With currently-available 20 TB drives, that's about 35 disks, which would fit within a few standard rack units (mostly depending on the size of disk you'd opted for). The total cost would be a few thousand dollars.
Digital media, particularly in the form of SaaS providers and Cloud storage, is an absolute trove of information on hundreds of millions or billions of people.