The origin of the word alone is very interesting:
The word comes from the Greek: οὐ ("not") and τόπος ("place") and means "no place". The English homophone eutopia, derived from the Greek εὖ ("good" or "well") and τόπος ("place"), means "good place". This, due to the identical pronunciation of "utopia" and "eutopia", gives rise to a double meaning.
Wikipedia
Its name alone then suggests there is no such place, that it cannot be created. It is an impossible idea that will not be realised - as a concept it can never meet its programme.
Therefore utopias are often associated with dystopias, the border between these two is fluid and often you can't tell one from the other.
A dystopia (from Ancient Greek: δυσ-, "bad, ill", and Ancient Greek: τόπος, "place, landscape"; or anti-utopia) is the idea of a society in a repressive and controlled state, often under the guise of being utopian. Dystopian societies feature different kinds of repressive social control systems, various forms of active and passive coercion.
Wikipedia
Utopias are known to be secluded communities/places, enclosed and separated from the world outside. This seclusion, regardless of its intended function, effectively becomes a tool of control and these places turn into dystopias as access in and out of them is difficult, if possible at all...
