I long thought there to be an odd Protestant fixation on the 10 Commandments verging on a temptation to legalism.  But after having assisted at Ordinariate Use Masses, where they may be recited before the Kyrie, I have a new appreciation and suspect that the fixation (from a Roman Rite perspective) isn't so much Protestant as it is English.  It still struck me as odd that Catholic parishes would post the 10 Commandments but on thinking of it, why not?  It looks like the point is clear.  Moreover it could serve the evangelization of Protestants.