Without copyright, the GPL wouldn't need to exist because the freedoms it protects would be impossible to suppress.
Absent IP, ceteris paribus, you'd run as much code as possible on your servers and obfuscate what you deliver to a client. There would be an entire industry in producing technical DRM.
Obfuscation only gets you so far. But faithfully recovering the original source code is not really the point. Even heavily obfuscated code is useful and can be worked with since in the end the program is still doing what it's supposed to do.
Those other licenses do not require republishing, so it seems that authors of OSS value the additional republication requirements provided by the GPL license. Even in under the current copyright regime, one can (perhaps other-than-legally) decompile binary to recover source-like code, and then launder and reinject the learned improvements back into the open source project.
And the GPL license does not universally grant patent rights back to the source project.
The FSF believes that closed-source software should not exist at all. Their license is explicitly designed to make it completely incompatible with closed source software. Updates to the license (GPLv3, AGPL etc) are specifically designed to close loopholes which closed-source companies were exploiting.
OSS by contrast sees Open Source as a public good, but lives in a world that tolerates closed-source entities. It's possible to use an MIT licensed gzip library in a closed-source program, with GPL you cannot.
OSS says "Open Source us better, but closed Source is better than nothing." The FSF says "it should be Free, or you should not use it at all."
Both OSS and Free licenses mandate that users should be able to build binaries from Source. If I make a change to the gzip library then my users are entitled to those changes. (There's no "giving back", only giving forward.)
It's still a form of proprietary lock-in similar to not offering data export, but it's not an unsurmountable hurdle anymore.
Why not? You can decompile a cookie to try to see what method was used to make it, but Nabisco or whoever still treats that method and the ingredient ratios as trade secrets. In fact, the whole idea of trade secrets are things that are kept secret because IP protections don't cover them.