“Harm” isn’t really the issue. In the Catholic and Orthodox Churches, the guidelines — the correct word may be “rubrics”, but I am unsure about that — are strict about who should read the Gospel. The Gospels — again, readings from Matthew, Mark, Luke, and John — are to be read by Priests (or bishops, etc.) or deacons, not by nuns or laypeople. The issue isn’t “harm”. These rules are decided or changed by the Vatican/Councils, not by fiat of individual Cardinals or bishops. Of course, when individual bishops do whatever they please, non-Catholics and Catholics who either don’t know the rules or resent them, ask, “What’s the big deal?” Well, I could ask what difference it makes if an Orthodox Jew eats a ham sandwich...but I wouldn’t ask that, because I understand that there is a logic underlying rules and there is a process to changing rules that make the rules more complicated than just whether one person should be “allowed” to chomp on a ham sandwich.
Seems Roman Catholicism has set up yet another "tradition" not substantiated in Scripture.
Roman Catholicism can do what it wants...it's just there is no Scriptural prohibition against a regular person reading the texts aloud in church.