It may be divorced from political reality, but it aligns perfectly with environmental reality. Sprawl is absolutely terrible for the environment, for a large number of reasons.
That said, I do think banning them (even just by developers) is unnecessary if you provide zoning incentives instead. If you give developers the option to split up land because it will give them a higher return, they're typically quite quick to do that, at least in Australia. That wouldn't prevent owners or speculators from building their dream standalone house.