The anus is a very sensitive zone, with lots of nerve endings.
Because this area is very sensitive it’s completely logical people stimulate the anus to get excited. There are even people who can climax from anal stimulation alone.
In the Netherlands about 30% of the adults involve the anus in sex play. Of the people between 12 and 18 years only 3% has experience with anal sex.
Many people have never thought about anal sex because they have a negative attitude towards the anus and as a consequence never looked at it or touched it. They fear it’s dirty. But many like it once they have put aside the idea that it’s dirty and have given anal sex a try.