Here are a few very simple reasons.
When I was still toying with the decision of whether or not to come home, I went to my first Mass at the Carmelite Monastery. I was late and walked in during the Gloria from the Missa de Angelis. It was like being dropped into another universe. Although this was a Novus Ordo Mass, it was celebrated ad orientem, as are all the public Masses at the Monastery. I had never experienced a Mass with such mystique. Try as we might, none of us can comprehend how simple bread and wine become the Flesh and Blood of the Divine Savior. Why shouldn't the way in which the Mass is celebrated be redolent of mystery?
Every time the newly-ordained deacon at our Novus Ordo low Mass crosses the tabernacle, I want to yell: "For the love of God, man, GENUFLECT!". This is never a problem at the TLM. No one ever crosses the tabernacle without reverencing the Divine Presence. When you allow people to receive Holy Communion in the hand, with as much reverence as you'd dispense a potato chip, isn't it any wonder there is so little respect for the Blessed Sacrament? When you treat the Eucharist as though it's an every day object to be taken for granted, people soon react that way. This doesn't happen at the TLM.
The music we hear at Mass should lift us to the Lord, not attempt to drag Him down to earth. There is zero chance you will hear "On Eagles Wings" at the TLM.
The ladies who regularly attend our TLM are as well-dressed and beautiful as any I've seen anywhere and they manage to do this without unnecessarily exposing themselves or causing a distraction in any way. Same for the gentlemen. Priests have enough trouble with the devil knocking at their door constantly. Why would any woman dress for Mass in a way that is provocative and could lead others, including the priest, into sin? The men leave their false idols at home on Sundays. No baseball caps or t-shirts sporting their favorite team. No sir. The focus is rightly on the Lord.
Maybe I'm imagining things, but it's seldom that a parent has to take a screaming or disruptive child outside at the TLM. I marvel at how quiet the two young children who sit in front of us each week are. If I didn't see them in front of me, I'd never know they were there. And their mother never has to pull out Cheerios or a sippy cup or any other amusements for them.
Our pastor has taken to celebrating the usual 7pm Mass on the evening of Feast Days in the Extraordinary Form, rather then the Ordinary Form. Every once in awhile, Novus Ordo regulars will attend and behave as they do normally, meaning they yak it up before Mass. But the dead quiet surrounding them soon lets them know they're out of place and doing something wrong and before long, the chatter subsides. If only they would carry this into the Novus Ordo with them. People behave as though they're leaving a bingo hall. This simply doesn't happen at the TLM. People greet each other outside the church, but they leave in silence so those who wish to make their thanksgiving after Holy Communion and Mass may do so in the sacred silence.
"The Lord is in His Holy Temple. Let all the earth keep silence before Him".