You're wrong. They're not required.
If you mean they SHOULD be required... that's arguable. Certainly there are lots of worthy pieces of musical theater that go unrecorded, and it's a shame. That's because musical theater albums don't make their production companies enough money... sales aren't widespread enough at this day in age. While some recordings do very well for themseleves, musical theater albums are not too bankable overall.
Not EVERY show ever made everywhere could OR should be recorded... that would be like saying every Joe Schmo with a band in his garage should be recorded. However, I see what you're saying: definitely theater recordings are wonderful, and should be recorded, if they have merit, regardless of potential financial gain. In a perfect world.
[title of show] on Broadway. it's time. believe.