VANCOUVER | Public Transport

[officedweller]

Where noise is a concern, they'll install sound barriers along the guideway.

I agree that the primary reason would be to prevent the guideway from towering over the streetscape. The main factor that ameliorates the presence of the guideway is having it located on the side of the street - not in the middle. That allows smaller station houses that do not dominate their surroundings too much. If the guideway was in the middle of the street, it would have to be taller to fit a mezzanine level under it to access the stations - that would have meant a larger structure and excessive shadowing on the street.
From the pics, you can see that the guideway does not seem obtrusive when beside buildings.