BarryLS1: The Chareidim have not always controlled the marriage administrative system or other religious services as they haven’t always controlled the chief rabbinite or the religious ministry. Furthermore, the problem with allowing any rabbi to perform any marriage anywhere in the country is that such a system would allow pick-and-choose where an engaged couple that is of questionable halachic marriage allowability could simply find the most lenient rabbi in the country who will allow it rather than being required to engage their own local rabbi whose halacic decision on the allowability of the marriage would be binding.
