Before I answer this I need to clear up a few misconceptions. One of the primary misconceptions in the west is that the Kama Sutra is simply a sort of manual for tantric sex. This is totally false from both perspectives. The first, and perhaps most obvious issue with this is that the term Tantric is wrong in and of itself and completely anachronistic. The Tantra as a movement includes a wide variety of esoteric ritual practices ranging from asceticism to mandala to, yes, sex, but of course this sex does not resemble sex done for pleasure in most cases and informs a greater ritual practice done for various reasons. Furthermore, the Tantra as a movement emerged in the late Gupta period, sometime between 400 and 500 CE, some 200 to 500 years after the compilation of the Kama Sutra. The second big misconception is that the Kama Sutra is simply a manual for sex. This is part of the orientalist zeitgeist that surrounded its "discovery" by Europeans in the late nineteenth century, but in reality only one part of the greater work on Kama, or pleasure, one of the lower goals of Hindu society.
Of course, this does not mean that sex and eroticism aren't an integral part of the work as a whole, as it crops up all over the chapters. Eroticism, is given an ethical component as well, being called the "touchstone of virtue" and seen as part of the basis for the ethical lives of Hindus. Sensuality is seen thus as a part of the spiritual path which culminates in the path to Moksha which is practiced when one leaves youth and thus leaves the lower goals of Kama behind. The idea that it is simply a sex manual or a guide to "tantric sex" is absolutely false.
With those out of the way, we also need to discuss the historical providence of the work. The Kama Sutra was compiled base almost entirely on earlier material in the 2nd or 3rd century by a man called Vatsyayana. This period was a major shift in North Indian culture as the emergence of Puranic Hinduism was taking place and the cultural norms of Brahminism became more enforced, caste became immobile and more enforced. Thus there was a renewed interest in the Brahminical law books, Shastras. The Kama Sutra is, in essence, a Shastra rather than a Sutra in that it details how to behave and seek pleasure as a wealthy man in Indian society.
The book is thus directed at these wealthy householders, Wealthy Brahmins, Kshatriya, and even upper Vaishya. Of course, Brahmins especially were seen as needing to eschew Kama, being a lower desire, in order to achieve the higher Dharma, but for Kshatriya and Vaishya, it was seen as an integral part of the life of a householder along with his Dharma and his Artha. Women too were expected to pursue Kama, in part for the sake of men, but also for themselves.
Now for the juicy part, did people actually utilize the sexual positions on a regular basis? The answer is yeah, probably. Some of the more...interesting positions were likely pretty rare, but they were probably done at some point, but most of the positions listed are actually pretty common, at least in fantasy and imagination, but they way they are worded sounds exotic. For instance, when I say, "There are ten kinds of bite, known as: discreet [gudhaka], impressed [ucchunaka], pointed [bindu], necklace of dots [bindu-mala], coral jewel [pravalamani], necklace of gems [manimala], scattered clouds [khandabhraka], the chewing of the wild boar [varaha-charvita]..." it sounds completely bizarre, but this simply lists places and ways to bite in an erotic manner, but the discreet bite is simply a light bite that doesn't leave marks where as the impressed and pointed leave marks in different ways, and the necklace of dots is a number of hard bites in a line around the neck or sex. This is far more common than people think today, according to the Kinsey institute, 50% of men and 55% of women report to an erotic response to biting and since this study was done in the 50's the data may have changed with contemporary reports placing BDSM activities far higher than the Kinsey institue's reports. Furthermore, such depictions were not uncommon in erotic poetry in India, including the contemporary poetry of the Satavahanas.
Of course, there are numerous positions that probably weren't practiced often, such as the "Impalement" pose where a woman continuously brings her foot over her lovers head while he places himself in front of her sex, but Vatsyayana remarks that these require practice or are uncommon. It is also notable for depicting, without much dismissal, lesbian and male homosexual acts. There are really no reason to doubt that these are anything but factual, as they, for the most part, do not go out of their way to demean the practice, despite attitudes towards homosexuality in classical India being largely negative.
There is also depictions of these positions, while not in the work itself until the Mughal era, in sculpture and in relief on temples and the like. This gives us visual evidence of the practice, even if here it was idealized as practiced by devas and yakshas and so on.
#Works cited
Banerji, Sures Chandra. A Companion to Sanskrit Literature: Spanning a Period of over Three Thousand Years, Containing Brief Accounts of Authors, Works, Characters, Technical Terms, Geographical Names, Myths, Legends and Several Appendices. Delhi: Motilal Banarsidass Publishers Private Limited, 2016.
Danielou, Alain, and Vatsyayana. The First Unabridged Translation of the Kama Sutra. New York: Park Street Press, 1994.
Doniger, Wendy, Sudhir Kakar, and Vatsyayana. Vatsyayana's Kamasutra. New York, NY: Oxford University Press, 2002.
Ganeri, Jornardon, and Peter Adamson. "History of Philosophy In India." History of Philosphy Without Any Gaps (audio blog). https://historyofphilosophy.net/.
Shelling, Andrew. Erotic Love Poems from India: Selections from the Amarushataka. Boulder, CO: Shambhala Publications, 2004.