The only way that I can remotely see it, is because in the blog post about what people get for free, here, the devs explicitly mention:
"So this is what we mean when we say Expansion Packs for KSP. We’re not talking about small content bundles, we’re talking about major game-changing sets of features, like Multiplayer, or Colonization."
In the release notes for KSP2, it specifically says that this version will bring: Colonies: Brand new to Kerbal Space Program 2 are colonies..
And: Kerbal Space Program 2 will build on the beloved modding capabilities of the original game, as well as deliver on the long-requested addition of multiplayer
Only because of these two things, I could see how some could argue, "But these are things the devs mentioned we'd get for free." I agree that I will purchase KSP2 no matter what, but to ask "How can people even ask this?", I can see both sides. By the way, I'm not one of the people expecting to get it free (although I wouldn't deny it if they want to give it to me) and am just waiting on the "Add to Cart" button; It's already in my wishlist.