Feeling obligated to return a favor, share resources, trade an item, etc.
If the game allows you to share resources, trade items or send gifts to your friends or other players then it may be using the dark pattern of Reciprocity. The person who receives your gift may feel a sense of obligation to return the favor. They may not have resources to share, and so they may feel bad that they gave something valuable away, or they may feel shame or guilt if they do not reciprocate. These unwanted negative feelings make the game less enjoyable.
If a game allows players to band together into guilds or clans, then sharing resources may be a requirement for participating in the group. Players may be punished by the leaders for not pulling their weight and helping out the team by donating valuable items.
The social pressure to donate items to other players means that you are giving up some of your own valuable resources that you have spent time and maybe money earning. This means that you have to spend more time and money to earn those items again.