Stars convert mass into photons over their lifetimes. The hydrogen fusion process converts about 0.7% of the mass involved into photons in a typical [sun-like] star. The amount of mass available for fusion in such a star is about 0.1 solar masses, so we can conclude that about 0.07% of the total mass is converted to photons over the lifetime of a typical sun-like star. This, however, fails to account for mass-energy conversion in the infant universe, which produced the CMB photons. The baryon asymmetry of the infant universe is estimated at about 1 part in 10 billion. Since matter-antimatter energy conversion is virtually 100% efficient, the matter that survived to become stars was only a microscopic fraction of the initial mass budget of the universe. While black holes may recover 99.9999% of all matter that remains after mass-energy conversion processes have ended in the universe, I doubt they will recover 99.9999% of all photons emitted over the history of the universe.