The most annoying thing about the 1976 Copyright Act is that copyright is only nominally automatic. To be clear, it casts a huge shadow over all creativity that would have otherwise been uncopyrighted. But on the other side, there's still a registration system. You need a registration in order to sue infringers, and you don't get statutory damages on infringements that happened before registration[0]. This trips up loads of creatives, and especially photographers, because it's a lot of boring bureaucracy that never gets explained to them up until they've already talked to a lawyer who says "no you can't get $$$ out of this big company that used your Facebook uploads without permission, because copyright lawsuits are never worth pursuing without statutory damages on the table".

The cruel irony of US copyright law is that, while we only half-implemented Berne, we still use Berne as a thought-stopping cliche for why we can never claw back copyright protection from the half-dozen publishers and creative artists that actually benefit from owning your childhood. Because the base assumption of copyright is that only the creative upper class is worth protection. Protecting artists as a class requires syndicalism and mass unionization, not atomizing everything into individually held psuedo-property rights that are financially ruinous to assert against anyone who won't fold immediately and settle.

The orphan works problem you're talking about is deliberate. Publishers like the idea that when they knock out a less-scrupulous competitor, their creative works spill out onto the ground like Diablo loot, and they can collect all that up and just idly hoard it forever. At the very least, a work that nobody knows how to license or can't afford to license is a work that has been taken off the market and can't compete with them.

Funnily enough, GitHub repos without a LICENSE file are covered by a fallback license in GitHub's ToS that basically says you're allowed to fork and PR. They've probably also explicitly added a "and we can train GPT on your code too" EULA ruffie in there too.

[0] There is a short grace period for this, of course. I think it's 90 days.