The faster it is, the more useful it is.

Most people need to drive an hour to get to the airport and you need to be there a recommended hour ahead of time for the security theatre, a possible half hour wait for you checked bags, and another hour to your hotel in most locations. That's three and a half more hours on top of how long your flight takes!

So that flight from Toronto to Montreal, even though the air time is only a little over an hour, home-to-hotel is actually more like 5 hours.

At HSR speeds it is less than 2 hours travel time and the train stations are in town rather than an hour outside so home→station and station→hotel is 15 minutes, 30 at most on a bus from the edge of town? So three hours at the most. And no damnable security theatre lines like at the airport!

Hyperloop (when it's finally possible) speeds would cut that trip to 90 minutes max. Imagine living in Montreal and commuting to Toronto for work.