Some countries that built extensive HSR networks (Italy, Spain, Japan) have a lot of challenging terrain. If you travel, say, from Rome to Florence by Frecciar

Some countries that built extensive HSR networks (Italy, Spain, Japan) have a lot of challenging terrain. If you travel, say, from Rome to Florence by Frecciarossa, the line goes through six galleries of total length of some 40 km. Human settlements are a bigger challenge. People don't like to be uprooted, and small communities along the way don't benefit from HSRs, so they have an incentive to oppose them.