Scale is a big part of it.

Every minute, 500 hours of video are uploaded to YouTube.

Even Google can't afford to run the biggest baddest model on every single one of those hours.

Though they do have the money to generate terrible TTS audio for many videos. And since google can't fathom a person knowing a foreign language, use those automatically without warning.

I've even seen videos that were in English, but mislabeled, so they got auto-dubbed back to English, replacing the real voices with a monotonous synthetic voice.

I appreciate the auto translated captions sometimes as they let you get the gist of what's going on, but auto dubbing is pretty much never desirable

They should just do it on the subset with the most views.

That makes sense actually. Re-sub videos when they cross a million views for example.

Or, cynically, for creators who pay an extra fee.

YT's business model is monetizing creators' output. Producing a video that gets a million views and generates a bunch of ad revenue is the fee.

I thought so, too. But they also let you create AI dubs of your videos into an arbitrary number of languages?

opt-in vs opt-out

I also suspect that the quality of transcription depends on the popularity of the video. So maybe it's decent for videos with 000,000s of views. Same way the video codec is changed from AVC to VP9 - and occasionally AV1 nowadays.