That is part of the DMCA (the act, not the "DMCA notice" often shortened "DMCA"). In exchange for not being liable for the copyright infringement ("safe harbor"), the service provider (here YouTube) has to act on notices right away. The user files a counterclaim if that was wrong.

In short, it's not YouTube's (or GitHub's, etc) call, this is part of the agreement with copyright holders (the DMCA copyright law).

Don't take that as an endorsement though, I hate the system as much as you do.

They just don't care. They're not a public service altruistically serving their users' videos up until the point the law requires them to take it down. They're an ad platform, trying to serve ads and not get sued.

Content ID was born out of a desire to keep Viacom happy after Google got sued: https://en.wikipedia.org/wiki/Viacom_International_Inc._v._Y...

Money, dear boy. They gain a lot more from keeping the big media companies onside than they do by pissing off a handful of creators (who are frankly a commodity to them).

Because the alternative is staring down billion-dollar lawsuits from Viacom and other copyright holders.

IIRC, it's because they got sued, and content ID was part of the settlement.