Yet again this morning I struggled to pass someone walking ahead of me. Every time I moved up get past, they drifted across and almost bumped me. I have experienced this numerous times. What is the reason? Do the earphones somehow affect balance? Is it that their attention is elsewhere and they are oblivious to wandering from side to side at random, implying presumably that we all do that if we are not focused on our walking? Is it that we normally rely on hearing a person behind us to cause us walk straight and give them a chance to come past? Or something else? It's rather annoying.