I disagree that's the point. The point is generally to distract oneself or to keep focus. Neither of these two reasons preclude the willingness to stumble into s.o. actually worthwhile.

Whether earphones are supposed to serve as a sign to keep away depends on the culture and gender. In the States, for instance, people are way more often stopped by s.b. on the street than in Europe. The idea that s.b. would try to sell s.th. or preach to you on your path almost every day is very foreign to most Europeans.