Is it a practical way to show the presence of Christ? Yes, but not only.
Burning it usually gives a red light. In every church. In Scotland, in Europe, or even in the wider world. The eternal lamp. One or two, placed near the tabernacle with the Blessed Sacrament, it signals to those who do not know the particular church where best to kneel for prayer. And everyone visiting, not always with an intention to pray, are reminded: here is God; here is the true presence of Jesus Christ. Show Him respect. Genuflect, kneel down, make the sign of the cross. Or also stop and pray. Whether it’s a fleeting visit or a longer stay; reciting the words of learned prayer or pouring out your heart to God. Pray, you’ve come to the right place, this is a good place for it.
But this lit lamp is not just a technical way of showing the presence of Christ. Burning day and night, not knowing sleep, reminding: “he who watches Israel will neither slumber nor sleep”. Not slumbering nor sleeping the One who promised to remain in His Church, who is always there to the end of the world. Not only under the appearance of Bread but also in His word, in the community of the faithful and also in the priest celebrating the sacred rites. He always is, always watches, always remembers. He is also my hope, my protector in all adversities. He watches over my life. He never forgets about me, never forsakes me. Yes, never slumbers or sleeps, the One who watches over Israel, over the Church and over me. He is the shadow at my side: The sun shall not smite you by day, nor the moon by night. The Lord will keep you from all evil; he will keep your life. The Lord will keep your going out and your coming in from this time forth and for evermore.