[ggcdn]

Rigidity is good for some things and bad for others. In seismic design, inertial forces tend to decrease as structures become more flexible (Good!). But the consequence is that things move more (Bad!) meaning that all the nonstructural things get damaged - drywall, chimney, ceilings, etc. If things move too much, they also are subject to various types of degradation - yielding, fatigue, etc.

The other structural aspect not mentioned in the above discussion is strength. You can trivially get an order of magnitude more strength than required by even the harshest of loads using steel in a small structure like this. The same cannot be said about wood. For instance, a single 3/4" A325 bolt will be able to resist about 40,000lb shear or 70,000lb tension. The entire base shear of this size of structure in a code-design earthquake would be somewhere around 4,000lb.

[ggcdn]

[clarification: I mixed up my unit conversion. A 3/4" A325 bolt resists ~25kip shear or 31kip tension. One of the joys of working in an industry that primarily uses customary units, while codes are written in SI units]