If the vinyl albums exists it is fairly easy, although time consuming, to convert them to digital. Tape only became widely used in audio recording in the 1950s and only a few of the big companies kept serious archives of their tapes. It really shouldn't be that surprising that the original masters for most music produced before, say 1980, have deteriorated or are just lost. Fortunately vinyl is a superb archival medium and the results of vinyl to digital transfers can be very high quality. If a vinyl recording had even moderate distribution existing copies can nearly always be found. This is true going back to the 1930s, but there are exceptions.
The situation for movies is far worst. It's estimated that 90% of all silent movies and half of all sound movies made before 1950 are lost.
