I think I'm trying to say that you're as likely to get abolition as you are a term of copyright shorter than has ever existed in the US, so why not shoot for the moon?

Because it's not clear that short copyright terms are harmful. Modern copyright shouldn't make us lose sight of the goal of promoting "the Progress of Science and useful Arts". 15 years is a reasonable starting point for achieving that aim. If it's still too long it could always be further reduced later.

You're as likely to get abolition as you are to get a 15 year copyright, which is ~1/4 what copyright was in 1909.

To be fair, at the founding it was 14+14, so 15 years absolute isn’t without precedent.

But I agree about the modern political situation around copyright.

I don't think so. Vast majority of creative works fall out of favor in the first 15 years of publication, so creators wouldn't be giving up anywhere near as much as if copyright was totally abolished. The situations are not comparable in the slightest.

Then their creators can released them under a lenient license, or to the public domain. Why do we get to decide for them?

I mean, we get to decide for them because copyright is an artificial limitation imposed by law on society to benefit creators.

It is a compromise between society and creators that is codified legislatively. We get to decide “for them”, because it’s an agreement between them and us (where the “them” and the “us” are actually both just the body poltic).

It’s a mistake to think of copyright as the natural order of things. It is a legislative creation, with the specific purpose of encouraging works entering the public domain, which is why we get to decide.

Because we're the ones granting them a temporarary monopoly in the first place.