Because this happened to me yesterday. And I saw a post on Linkedin a few days prior where it had happened to someone else too. This is what happened to me;
I walked up the road on my own to go to my sons' house 5 mins away (they live with their dad, older child has cerebral palsy and needs care, I spend the days with them). Live in a not rough neighbourhood (not posh, but okay). A group of about 7 men and women in their early 20’s, carrying a speaker playing loud Grime walking towards me. Something a bit menacing about them, didn't move over a bit like you'd normally expect so I had to walk on edge of pavement. I thought I was just being paranoid because everything's so weird right now, but as I walked passed them one of the young men deliberately coughed towards me to the amusement of his friends.
I do hope this is not becoming a thing.