Tags are used for the convenience of searching for all videos of a common segment. All videos that are similar to each other are united by one tag.
For example, if a video contains sex scenes on the street, in a park, in a forest, then such videos are combined into a common tag – sex on the street.
Firstly, tags are the standard and trend of recent years. Secondly, it is very convenient.

Brother and sisterHotel sexMasturbationOutdoor sexSex for moneySex on cameraSex with a neighborSex with nurseSex with teacherSex with wife