Many Tantric practices, do not involve a literal union of two people, though they are based in the symbolic synthesis of male and female, solar and lunar, compassion and wisdom. From duality to oneness.
In the West, there is a great misunderstanding of the actual techniques and purpose of Tantra. While most Western Religions condemn the body and the sensual and sexual energy as a form of temptation or sin, Tantra recognizes the sacred wisdom of the body and uses sexual energy as a propellant into spiritual transcendence.
Because of this radical deviation in the way of viewing sexuality, people began to classify Tantra as a practice of sex in and of itself. It’s very similar to the misconception that yoga is a physical workout to tone your body rather than the original purpose of yoga.
Tantra is not a practice in sensual indulgence but rather a practice of the transmutation of sexual energy into a higher and total embodiment of the energy. It is a comprehensive spiritual practice not to be simplified or done the disservice of this type of misclassification.