The REALITY of God, not metaphorically, spiritually or symbolically, but Physically and Divinely present in the Blessed Sacrament, is why genflect. I just copied this from something called “Genuflecting Do’s and Don’t’s”.
We genuflect to the Blessed Sacrament (NOT to the altar, to a statue or to the Crucifix).
It’s only necessary to genuflect when entering and leaving the church, not every single time you go out of the pew.
Bend on one knee, the right knee, and it should actually touch the floor (health/age permitting).
It’s not necessary to make the sign of the Cross, but permissible if customary.
If moving about the church for activities, etc, a slight pause before the crucifix or altar, with a bow of the head is respectful. This is of course not the same as genuflecting, but a way to be attentive to God’s presence and maintain a reverent atmosphere.
When the Blessed Sacrament is exposed (Adoration, or as some now call it “Exposition”), we enter the church and genuflect on BOTH knees, and then enter the pew. When leaving, also fully kneel on the ground, bow the head and then rise to leave.
Also, some people come to church now but only stand and bow their head and then sit down. They do not genuflect. Unless age or infirmity prevents genuflection, this is wrong and disrespectful to the Blessed Sacrament!
No genuflecting is done if there is no Tabernacle (such as in some Chapels) or on Good Friday when the Tabernacle is empty