Genuflection is a sign of our adoration of the divine presence in the Blessed Sacrament reserved in our churches. Today, many churches have a Blessed Sacrament chapel outside of the main sanctuary. Therefore, in these cases, the generally accepted proper procedure is to bow to the altar (as we do on Good Friday) instead of genuflecting.
However, if one wishes to continue to genuflect, that is acceptable also. Wherever the Blessed Sacrament is present, genuflecting is the appropriate form of veneration.
There are other reasons why you don't see as much genuflecting. It is no easy task to bend the knee (the meaning of the word genuflect) and keep one's balance. Many of our churchgoers are getting older or otherwise have health problems which may prevent them from genuflecting. In such cases, a bow would be appropriate. On the other hand, most people kneel when they go into the pew as they have support of the pew in front of them. So, they express their adoration then.
However, there is no doubt that at times the failure to make some gesture of reverence on entering the church is due to our lack of attention to the place we are entering.
It would be good to reflect a bit on the meaning of this reverential practice. Kneeling and genuflecting are among the gestures that have been part of our religious custom for many centuries. Others from the earliest day of the Church have included bowing, raising the eyes or hands, prostration, folding the hands, striking the breast.
Bowing is a common reverential sign, especially in Eastern Christianity, where deep bowing usually replaces genuflecting. These are symbolic of our humility, of our smallness before the greatness of God. They show our respect for the presence of Christ in the Eucharist and for the altar where Christ is made present during the Mass.
Many of these gestures were borrowed from court etiquette. Genuflecting and bowing are a modified version of prostration which was common before an idol or a divinized ruler. Today, we still see prostration at the ordination of priests. It seems that only in the 16th century did kneeling or genuflecting in the presence of the Blessed Sacrament become common.
Why do we use some of these gestures? Basically, they stem from our need to express ourselves fully in prayer, whether they be prayers of adoration or gratitude or penance or supplication. We are human beings and as such, our bodies are very much a part of who we are. When we look at the Scriptures, we see Jesus praying with bodily gestures. Our body and our emotions can help or hinder us when we pray.
We can pray sitting, standing or kneeling or even lying down. In private prayer we choose the one which is most conducive for prayer for us. For example, if we are in a posture which causes pain, we will be focusing on that part of the body rather than on God. Or if we are careless with our postures that can affect how we approach prayer.
In our worshipping communities, we use different postures at different times. These are meant to aid our recollection and prayer. In the same way, a genuflection or a bow when we enter the church can help focus us toward the sacred action which is about to begin.
If we fail to make any sign of reverence because of our inattention or haste, we need to become more centred and reflective as we enter our places of worship. This will help us to enter into prayer and into our community celebration of the Eucharist.