Because my pastor explained to me today that kneeling was merely a custom, and insisted that standing during the Eucharistic prayer could also be revential:

Standing during the eucharistic prayer at Mass in US dioceses is permitted "only on exceptional and extraordinary occasions ... and never on a regular basis," the US bishops' Committee on Liturgy said in its latest newsletter.

The committee's September newsletter, made public in mid-October, said "the only licit posture" during the eucharistic prayer is kneeling, unless Catholics "are prevented on occasion from kneeling due to 'health, lack of space, the large number of people present, or some other good reason.'"

The newsletter was quoting from the General Instruction of the Roman Missal. 2002 CNS Release

And in case you wanted to see it, here it is in the Roman Missal:

The faithful should stand from the beginning of the Entrance chant, or while the priest approaches the altar, until the end of the Collect; for the Alleluia chant before the Gospel; while the Gospel itself is proclaimed; during the Profession of Faith and the Prayer of the Faithful; from the invitation, Orate, fraters (Pray, brethren), before the prayer over the offerings until the end of Mass, except at the places indicated below.

They should, however, sit while the readings before the Gospel and the responsorial Psalm are proclaimed and for the homily and while the Preparation of the Gifts at the Offertory is taking place; and, as circumstances allow, they may sit or kneel while the period of sacred silence after Communion is observed.

In the dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus until after the Amen of the Eucharistic Prayer, except when prevented on occasion by reasons of health, lack of space, the large number of people present, or some other good reason. Those who do not kneel ought to make a profound bow when the priest genuflects after the consecration. The faithful kneel after the Agnus Dei unless the Diocesan Bishop determines otherwise.53

With a view to a uniformity in gestures and postures during one and the same celebration, the faithful should follow the directions which the deacon, lay minister, or priest gives according to whatever is indicated in the Missal. GIRM

Alright, alright, I'll do it. I'll kneel at every mass, even if nobody else does. I'll pray that I stop being so fearful of going against the grain when I know I'm doing the right thing.