Having dedicated bike infrastructure means that people using bikes and pedestrians are not forced to compete for a tiny strip of sidewalk while most of the roadway is dedicated to cars. Bikes need to yield to pedestrians, so aside from it being illegal to ride on the sidewalk as an adult, it is much slower. There are also many roads that do not have sidewalks.
Proper bike infrastructure is protected by concrete bollards or curbs
Having dedicated bike infrastructure means that people using bikes and pedestrians are not forced to compete for a tiny strip of sidewalk while most of the roadway is dedicated to cars. Bikes need to yield to pedestrians, so aside from it being illegal to ride on the sidewalk as an adult, it is much slower. There are also many roads that do not have sidewalks.
Proper bike infrastructure is protected by concrete bollards or curbs