Why are react, react-dom, styled-components dependencies, not dev and peer dependencies?

[dwjohnston]

Given that the intention that these components should only be used by other projects, shouldn't react, etc be a peer dependency?

[ExLeonem]

Moving react and react-dom to peerDepencies would make sense. But I think styled-components should be kept under regular dependencies, otherwise users are required to install styled-components even if they don't use them.