It comes from the barbering world and is very old school. The historical record indicates that talc use goes back far, as when mining the fine dust from granite, sandstone, etc, or talc dust would keep the workers dry in hot miserable conditions. Come forward to Victorian era times, and water for bathing was only for the very wealthy and thus Parfums, EDT's, and other concoctions were produced to make you smell good, and the talc was used for a drying effect, and also added fragrance helped in the "funk smell" of the less than hygienic era
Barbers started using it to "seal the shave". It assisted with any inflammation in the pores and much of the talcs of the day had menthol to cool your face and neck down in the hot, humid summers. So the tradition of using talc is a time tested and honored practice, in mine, as well as, most barbershops. I continue it to this day, as it is an "old school" sign of true barbering IMHO.
More recently the "talc" in most powders was allegedly termed as carcinogenic , which has never really been proven , so talc use did dwindle, until more talc companies found that a cornstarch base worked almost as well. Come forward to now, and it is used to seal the shave, bring some smoothness to the shave, hide a bit of imperfections on the skin, such as abrasions, and to also give your skin that silky feel. At home it is used more to get that "Barbershop" feeling. Plus used everywhere, the powder prevents what we in hot weather and humid climates refer to as swampazz, greasy burrito face, or whatever you determine fits your skin type, LOL. So it is a moisture control as well, and keeps you dry, as it does counteract the effects of Sebum ( the oil in your pores, that lubricates your skin )
there are still some old school talcs from Eurpoe that use Talcum in their powders, but most have moved to cornstarch. Talcum was banned in 1980 in some countries, with strong suggestions to not use do to asbesto found in them during the grinding of the rock. It is not banned in the US. It was determined that the amount of asbestos was so minimal it was not harmful. However, most have moved away from it, based on consumer groups blowing things up. J&J was the most attacked as their baby powder had the trace of the substance. The cornstarch is a better and more economical ingredient, and alleviates any questions of safety
Hope that explains and please feel free to ask more
