Both the British monarchy and the Irish presidency work well and meet the needs of the respective states. Both have one example of one unsuitable head of state during the 20th century and both were reasonably promptly forced to step aside. President Higgins is greatly loved and there were the two phenomenal Marys that preceded him.

To democrats (with a small d) the idea of someone being born to be head of state is problematic, but the practical benefits cited by Davidg and the genuine love and support most Brits have for the Queen and some of her heirs at least, outweighs this in my mind and ultimately it could not survive if a majority of people did not want it to.

John