I'm afraid I have to take issue with you there, Alexandra. Catholic liturgy has always taken into account the fact that we humans have bodies with which to apprehend and respond to the world around us. That being the case, at various points in the mass we're required to sit, stand, or kneel, depending on the liturgical action. Sitting is the most passive posture of the three and the one that demands the least from us. Kneeling denotes humility and so is appropriate for those points in the mass in which our corporate prayer is the most intense, as in the eucharistic prayer. But in standing our bodies are the most alive - we're free to move, stretch, our blood is flowing more and oxygen is getting to the brain faster - all of which engages us more deeply with the liturgical action. When sitting it is easier to get lulled into a sense of complacency. These days it seems to spur distracted people to look at their cell phones, so there's something to be said for more standing, I think.