I recall reading that the pylons had vertical and horizontal dampers to protect against earthquakes (among other minor natural changes), so wouldn't those dampers be able to cancel out the shear waves?
Passive resilient systems could help with higher frequency vibration (above say 100 Hz or so, depending on the forces and weights involved), but for lower frequency vibration (especially below 20 Hz), the resilient elements would have to be so compliant that even a gentle breeze would create very high vibrations in the guideway itself, which would be incompatible with the speeds of the cars inside.
You could make the pylons so massive that the forces from the vehicles couldn't move it, but again you're talking about higher construction and material costs, as well as visual impacts.
edit: though, mind you, the whole capsule also has mechanical suspension