Not to argue with that, but we have generally become tolerant, uncritical, broadminded, etc. about so many things these days that in a time when it is thought stuffy to ask people not to wear shorts to church, it is not surprising that open communion would be common.
Not surprising at all, for such churches have secularized their services...
However, in the early church (which most denominations claim to take as their standard and guiding example) the Sacred Meal was not something to be served up to just anyone. In fact, aspirants--people studying to become church members--were required to leave the premises when the preparation of the Communion elements started, and long before the actual distribution.
In our monasteries, this is still frequently the practice... In our particular parish, which is traditional, we still call for all the catechumens to depart at the end of the first half of the liturgy, even though in fact we no longer observe the obedience for this call - When I was a catechumen, I departed, personal choice... And we love the fact that most of our women faithful cover their heads in services... Some do not, with no opprobium... We are glad they are here...
Rightly or wrongly, the belief was that this was a sacrament that, in addition to everything else (Real Presence, Memorial, whatever), was a true fellowship meal, a ceremony that was a bond between God and Man and also between the members of Christs church. It was thought wrong to distribute it to just anyone who walked through the door.
It is the Mystery of the Body and the Blood of our Lord... We not only will not give it to anyone not Baptized into the Church, and not guilty of any unconfessed and unremitted sin, but we also require a recent confession, and beyond this, the praying of the Prayers of Preparation for Holy Communion just prior to Receiving... And this because we know it is real, and we do not wish to harm those who might receive it in an unworthy manner - Not that we are worthy, but we act in obedience to the manner of Receiving Christ prescribed, as it has been handed down to us...
Most Christian Churches do not regard Marriage as a Sacramental Mystery of the Church, and then complain that the State is legallizing same sex marriages... And the same inroads are not being established regarding the must fundamental Mystery of the Covenant of the Body and Blood of our Lord...
Sometimes the Old Ways turn out to be the best ways...
Which have been practiced in all times by all in the Church...
Arsenios