We don't make people figure out how to domesticate a cow every time they want a hamburger. Or test hundreds of thousands of filaments before they can have a lightbulb. Inventions, once invented, exist as giants to stand upon. The inventor can either choose to disclose the invention and earn a patent for exclusive rights, or they can try to keep it a secret and hope nobody reverse engineers it.

The model already embodies the "total sum of a massive amount of compute" used to create it; if it's possible to reuse that embodied compute to create a better model, that's good for the world. Forcing everyone to redo all that compute for themselves is, conversely, bad for the world.