Tunneling has gotten efficient & cheap, so it can be easier than laying track in cities. That requires the state to seize private property via eminent domain or some such -- extremely unpopular -- and build grade-level crossings (bridges, underpasses) for street traffic congestion & safety.

Second, anyone tunneling today, these could be converted to reduced-pressure hyperloop-like transit in future if/when the technology matures. No tight turns...

And the people freaking out about earthquakes - sheesh, tunnels have been built and operated for thousands of years since ancient times, for mid-speed rail for 100s of years, and high speed for over 60 years. And we haven't stopped tunneling. One can reasonably conclude earthquakes aren't a big deal for tunnels, regardless of the speed of travel. Assess damage, repair & move on...