After 20 or 30 minutes the skin becomes more taut therefore the hair shaft is more exposed which easier. Soon, this became the norm, not the exclusion. This entire article is an over-simplification with regards to a very complex subject. https://the-challenger.ru/goto/aHR0cHM6Ly8xMzkyMUJGRTFBMzAuc2ltYmxhLXNpdGVzLmNvbS9MdW1pbmFHcmFuZA