How would your posture or speech change if your friend whispered, "Jesus is standing right behind you"? My back would suddenly straighten, I know that. I have shared many intimate moments with the Lord in prayer, and I know that He is present everywhere, but I couldn't help snapping to attention if I realized that He was physically standing behind me I would . Whatever I was in the middle of saying would suddenly lose all importance, and I would spin around on my heel as quickly as I could to acknowledge Him. I don't think I could take a step toward Him or reach out; I would be too transfixed. I would have to wait for Him to reach out to me.
It is this type of presence - Jesus' physical presence - that we experience in Catholic churches. Jesus is really present, in a physical way, there in the tabernacle where the Eucharist is reserved. And that is why we genuflect - touch our knee to the ground - before we enter our pew. It's the reason we stand, kneel, and maintain a reverential silence through the Mass. All our attention is fixed on Jesus, because He is present in the Catholic sanctuary in a way far different than He is anywhere else in creation - even in the churches of other Christian. (I mean no disrespect; Protestant brothers and sisters do not share Catholic belief in Jesus' Real Presence in the Eucharist, and so in their theology this level of presence is not possible before the Second Coming.)
This is why Catholic sanctuaries are much quiter than our Protestant brothers and sisters'. They have a wonderful appreciation of Christ present in the gathered assembly and they celebrate that in greetings and conversation. We Catholics need that kind of fellowship with the members of our parish! But for us it should take place in the entry way/lobby or over coffee and donuts afterward in the cafeteria. Within the sanctuary Christ is physically present to us through the miracle of the Eucharist - right there in the tabernacle. And if we truly believe that, then our actions should follow, as surely as if we suddenly realized He was standing right there behind us!