1. The altar railing separated the sanctuary from the rest of the church. Only the priest (wearing his stole) and the properly vested altar boys/acolytes could enter the sanctuary during Mass, and even between masses, only select ladies of the altar guild would enter to change the linens and put in flowers, etc. It was considered a holy area. One genuflected upon entering or leaving the sanctuary...even the priest did this. The tabernacle, always withing the sanctuary, was like the Holy of Holiest in the Jewish temple, ie. only the sanctified hands of the priest could open and touch the sacred Hosts and vessels in there. One always genuflected when crossing on front of the tabernacle.
2. The railing not only separated the boundary between celebrants and congregation, but provided a place for the congregants to kneel respectfully in submission to Christ while they received Holy Communion on their tongues. An acolyte held out a gold or silver plated paten to catch any falling hosts or crumbs.
Removing the railing does in my opinion seem to take away the focus/significance of the Sanctuary.
it would be nice to see it make a comeback.