Why utopias seems obvious, I think: Who doesn’t want to live in utopia?
Of course, you want to be careful here—inside every interesting dystopia there’s probably somebody who thinks it’s utopia—but as we’re talking about personal utopias, that doesn’t seem like a showstopper. Anybody who doesn’t want to live in yours doesn’t have to.
The more interesting question is why techno-utopias?
The answer to that is, because techno-utopias are much more “build your own” utopias than most other types.
Your own personal preferences might incline you more toward socialist utopias or anarcho-syndicalist utopias or eco-utopias. Maybe your utopia is tribe of hunter-gatherers or a village of yeoman farmers. But all those utopias require activity cooperation from so many other people that they’re probably impractical.
Building a techno-utopia, on the other hand, is entirely possible for one person or one family. And it’s possible right now.
Helping you do so is exactly what this site is for.