Why do AI chat interfaces (Grok, Gemini, ChatGPT) all look the same?

I had a few tabs open to various chat services and am struck by how nearly identical - font, colors, layouts - that Grok, Gemini, and ChatGPT look to one another. Naturally, I conversed with the AI's about this but they are gaslighting me once more, "oh, it's natural that they all look this way, it's the most efficient." Well, yes, but the VI editor is the most efficient but not all editors look like that. Can someone offer me a reasonable explanation?