In reply to Steve Grant.

Well now we know the effect of telling theme authors that they can't include blocks in their themes. Their customers want fancy blocks, no one knows which block plugins will stand the test of time, and theme authors can't trust and rely on block plugins by other companies, so they all make their own similar block plugins.

Isn't Gutenberg also trying to compete with Elementor? If these standard blocks are so popular, maybe they should just go in core, even if they seem a little too elaborate for that. Users will have consistency and won't have to choose between a zillion similar plugins, and themes developers will have a reliable source of fancy blocks and can focus on styles and patterns.