There are always some users on social media that annoy you or who you don't want to be part of your daily life at all.
Perhaps you've were in a heated argument with a partner and you're furious with him or her. Blocking them could be an effective way of showing that you're angry with them.
There are always scams on social media. Blocking these on the Cash is the most effective method to avoid these.
Cash app provides Block option for its users, however don't worry that you are able to also remove them at any time you want. Read more: how to unblock someone on Cash App