To undo what they have been taught all their lives. The Low Mass is not a catechism class. If you have ever been to a Low Mass (not saying you have, not saying you haven't), you will realize that there is minimal interaction between the celebrant of that Mass and the worshipers. It is quiet and contemplative. There is, at maximum, between 5 and 15 minutes of teaching (and the 15 minutes is if the priest has a relatively LONG homily). The rest is strictly quiet, contemplative worship. And if you don't understand what is going on (a/k/a the theology), you will just be there...doing the motions...and wondering what is going on, rather than worshiping in union with the priest and the whole Church.
The Pontificale and, to a degree, the High Mass, has enough pageantry and music to keep one entertained. And the Novus Ordo Mass is specifically designed to have crowd interaction. But not the Low Mass.
But for some this is enough...how can any judge the heart of that person sitting there? Jesus seemed to pay attention to people just "being there" and it is He who drew them out of the crowds and addressed their concerns.
I know of a man who attended church every Sunday...the only words from his lips were...Thank you Jesus. He knew who and what he was and who and what Christ had done for Him...it was enough.
I think it is wrong for those learned in the deep things of theology to look down on those whose humble trust in Christ is not sufficient. When we get to heaven the question will not be how much one has learned about Mass...but how much have they loved Christ.