Good point about trains. But I know one of the first suspension bridges did carry trains.
https://en.m.wikipedia.org/wiki/Niagara_Falls_Suspension_Bri... .When we bid for the Tappan Zee bridge, the community wanted us to design it to take trains in the future. (Our team did not get the project) . Not sure how the executed design turned out.
Actually there is very little stress on the cables. The cables are stressed just enough to take the sag out of em. i.e. All the cables are actually supporting is their self weight! All you need is a hand-held jack and a lot of clever math, to install them :-).
The deck on one side of the tower is held in place by counter weight of the deck on the other side.
About earthquakes, it's designed for those 100 year quakes, hurricanes and floods. When we were building the Audubon Bridge across the Mississippi River, we were in fact hit by a 100-year flood and 2 hurricanes. Other than some stored material floating away and having to watch out for alligators in odd places. We got through fine :-)
The bridge type is rarely chosen for beauty :-) especially when contractors have to bid competitively for tonget a chance to build them. Governing factors are technical feasibility (design and constructability) and cost.