Sure, authors can adopt Gemini-like restrictions on their own simple HTML pages to gain some of the benefits of publishing with Gemini.

But this ignores the benefit for readers. Simple HTML pages are one link, search, or change of management away from a sea of enshittified internet slop. But Gemini capsules never have banners, unwanted sounds, intrusive ads, popups, etc, making browsing gemspace a qualitatively different experience.

To use a metaphor, a gardener can plant the same flowers alongside a loud, busy, trash-strewn highway as they can in a quiet garden. Many more people will see the flowers along the highway and it's a wonderful contribution. But wandering amongst the flowers in a peaceful garden is a qualitatively different experience than doing so alongside a busy highway.