HEAR ME OUT BEFORE YOU DOWNVOTE.
Disclaimer: The hyperloop is an absolutely shit idea right now. I do not support building in any form right now.
Now to the shower thought: Theoretically, a hyperloop can get you from place A to place B on the planet in less than 40 min (back of the napkin calculations assuming constant acceleration and deceleration of around 1G). Being completely underground (more on that below), it would also be a really good piece of infrastructure safe from arial/orbital bombardment.
Now to the obvious problems: We need the tube to be very very straight to achieve high speeds without killing our passengers. We would want the hyperloop to enter city centers. Building such a straight thing in city centers would require a lot of demolition. Therefore, we would have to get it underground. Bringing it on the ground again outside cities doesn't make sense because we would be introducing steep upward curves, thus reducing its maximum speed. Therefore, it makes sense to build this thing completely underground. Building underground also gives us many more benefits like not having to do much land acquisition, safety from violent attacks and so on.
Our tube would have to be incredibly airtight. It absolutely cannot have any leaks anywhere. Also, we need to be able to achieve incredibly low chamber pressures and maintain them.
If we are building this underground, we would need a shit load of energy to dig and transport the material outside the tunnel. We would also need a shit load of steel and other resources for these incredibly long tunnels.
Where do we get this energy? Where do we mine these resources without destroying the planet? Now this is where the "future" part comes in. We would need energy to be incredibly cheap. The only viable long term method (by "long term", I mean it from the civilization time scale) would be via nuclear fusion. When is nuclear fusion happening? Well, it's only 30 years away! /s Jokes aside, the energy source might be when nuclear fusion not only becomes possible, but also incredibly cheap (the nuclear reactor shouldn't cost billions lol).
About the resources? Well, we probably need to mine them on the moon, no? The moon has A LOT of them right on the surface. If we can mine them and send them back home, we solve our resources problem!
Well, you might ask- doesn't it make more sense to just have spaceships with engines propelled by nuclear fusion that exit the atmosphere, go at hypersonic speeds and then drop in? Why build expensive underground continent spanning tunnels? Well, what if we are attacked by aliens? They could easily blockade our airspace. Hell, just dropping a few million stealthy pebbles in our lower orbits would be enough to stop all hypersonic travel (the risk of ships exploding on contact with these pebbles would be too high for air travel to continue). Hypersonic spaceships would also face the problem of traditional aircrafts- you would need to build spaceports far from city centers. These spaceports would require a lot of space and cause a tremendous amount of noise pollution (constant sonic booms for every launch and landing).
Therefore, I think I have made my mind. I think I would be voting for a hyperloop proposal that possibly would be tabled in our direct democratic government a 100-150 years from now!