For the most part, the most plausible states that could return to monarchy are the Balkan States, and even then some opted to remain a republic. The reason why Monarchy isn't popular is simply because, in the eyes of many in the modern world, they tend to see monarchy as a relic of the middle ages and people see Republics as a representation of what it means to be in the modern world.
A restoration of monarchy tends to be something that is very difficult, almost bordering on nigh impossibility, only being kept from being completely impossible because Spain and Cambodia were the only instances where a legitimate Monarchy has been restored from a republic.
Frankly, it's much, much easier to work to keep the monarchy going than to restore a monarchy from another government type.