>>11398476
Deer are the quintessential prey animal, and their tail tufts are their most iconic trait outside of their antlers. Mainly because the tail serves an important purpose IRL as a warning signal to other deer when a predator is spotted. Sex already has a lot of thematic parallels with predator/prey relationships (Sayings like "Men are wolves" or "Sexual predators", etc) so putting the iconic feature of a prey animal on a cute girls rump probably tickles the lizard brain in you that just wants to catch her, pin her down, and ravage her to your hearts content.