Predictability has value. For example because "we need to make a change to the route" type people are around, your bus line can be taken away from you. Becaus

Predictability has value. For example because "we need to make a change to the route" type people are around, your bus line can be taken away from you. Because tracks aren't moved as easily, people rely on them, plan around them and you get things like increased property values because (and overall higher quality of life, especially around tram lines) due to that.