Even if you don't, you have property owners whom you'll need to either convince to sell or you'll have to get eminent domain to cross their land. Across multiple jurisdictions depending on distance covered, any one of which could delay your project by months or years with procedural objections or hearings. You'll need environmental impact studies and accomodations for the entire route. And for high-speed rail you'll need to build underpasses/overpasses at every road crossing. And once you build a rail line you're pretty committed to that route. Air travel avoids all of that.