We do it because 21 September is a recognized day. We pick various days to mobilize human beings. There is more to do than hold a sign or make a blog post to make a difference, which is why we hold events to bring together people to talk, face challenges, overcome resistance, identify important roles. But on the Internet those messages just get sucked up into the ether, and are not so useful or effective.
The Covid pandemic has really limited the work that we can do to build, spread the word, and create the conditions to ensure Peace, Nonviolence, and the things that bring us all together. We hope to be back with Day In The Park next year.