1. Like animals: Some people may like animals like pigs and think they are cute, so they choose pig's head to show their love.

2. Sense of humor: Some people may think that pigs are animals with a sense of humor, so they choose pig's head to increase the interest of their social media.

3. Self-description: Some people may think that they are lazy, greedy and slow like pigs, so they choose the pig's head to describe themselves.

4. Cultural symbols: In some cultures, pigs are regarded as symbols of wealth, bumper harvest and good luck. Therefore, some people may choose the head of a pig in the hope of bringing good luck to themselves.

In short, the reason for setting the avatar to pig may vary from person to person, and the above contents are for reference only.