system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do opera singers put so much vibrato on everything? Is it the only way to get the volume they need?

Or just convention?
gpt
Voice major here...

Vibrato ensures a continuous airstream from your diaphragm. It's an easy way to keep your muscles from gumming things up in the throat/jaw area, which can change the sound. Having your muscles truly loose and relaxed while singing makes for a truer more beautiful sound, and vibrato ensures that the muscles don't mess up the airstream. It's a healthy way to sing that will preserve stamina, something opera singers need to get through 4 hours of Wagner.

True ELI5?

Vibrating their voice like that forces them to keep their muscles loosey goosey, which makes singing easier and more beautiful.