Why are hurricanes considered more damaging than tornadoes when tornadoes have stronger winds?

They aren't. Tornadoes are more violent than hurricanes. The winds of both hurricanes and tornadoes are driven by the pressure at the center of the storm being lower than that of the surroundings. Tornadoes produce a similar pressure drop to hurricanes, but over a much sorter distance. This means the pressure gradient is steeper, and the air is subjected to a greater force.