I don't believe anyone ever said that you can't charge for development. The only issue is that you're not allow allowed to limit people's right to distribute it. Once you already developed it and have given access to one person, it's up to them whether to pass it forward.

It's just like if you tell someone a joke. You can still claim credit for coming up with it, but not to stop its propagation.

In particular, you can still make money as a developer by asking for it upfront, whether from an employer, or patrons, or early access, or whatever model. Similar to how Netflix might pay someone upfront to develop a stand-up comedy special

I don't get where you get that idea of not charging for development.

That said, I basically never seen anyone charge for a distribution. I figured that people think there's no point, so they just don't.

Now, charging for development? That absolutely happens.

Exactly. It isn't really possible to discuss this without "copyright" and that is why RMS focused on that topic. Conventional commercial copyright in practice is making a monopoly of redistribution and then burdening the distribution cost with additional cost-recovery and/or profit-taking.

I charge for development of (F)OSS. It's my salary. My employer likewise charges the patrons/funding agencies. But we get paid once for the effort, like any usual labor contract. We don't try to get paid again when our past work products are copied.

In the old days, paying a distribution cost was more common for free software, when it actually took effort such as writing and shipping media. This handled the case where someone asked for a distribution, so that sharing did not become a financial burden. It's a mostly obsolete concept now with pervasive internet and many low cost or free hosting options to put content out there at essentially zero marginal cost to deliver copies.