I would prefer 10,000 service providers to one big one that gets to read all the plaintext communication of the entire planet.
As it stands, I have a bunch of photos on my phone that would almost certainly get flagged by over-eager/overly sensitive child porn detection — close friends and family sending me photos of their kids at the beach. I've helped bathe and dress some of those kids. There's nothing nefarious about any of it, but it's close enough that services wouldn't take the risk, and that would be a loss to us all.