I disagree, many of those decisions were based on what would be more practical and economical but this idea would be both!
Aside from the engineering hurdle of setting the system up, it would be cheaper per passenger than the airlines, it would be completely immune to the weather, it would be completely silent because there would be no air in the tubes or any friction during travel, and unlike the 70's there's a growing need for such a system.
Traditional transportation options are getting less affordable, the need to commute to work, etc. is increasing in many area of the country as jobs are harder to find and get to. The aging metro railways are getting harder to maintain and the country really needs to develop more to keep up with other nations that are developing bullet trains, etc.
Besides, improvements in speed aren't always straight forward but they do still happen...
Take some of your examples for instance... A F-22 may only be able to go up to Mach 1.6 but it does so with Super Cruise, which means without Afterburners and on engine power alone. A F-14D in comparison could only reach Mach 1.1 without afterburners!
While there are other reasons why top speeds haven't been exceeded yet, like modern jet fighters don't all have the same combat role as they used to... F-22 will strike with much longer range weapons than a F-14, and the F-22 is also more maneuverable, as well as relies more on stealth!
Stealth especially is a factor because previous stealth fighters were sub-sonic but now they can be super sonic...
So basically, they went with what was more practical... but that doesn't mean things didn't improve... Even though what's more practical depends on both what can be done with existing technology and what is the easiest application of that technology.
The Concord for example was deemed not worth it because the application was not very practical... Super sonic crafts are not allowed over populated areas and thus the Concord could only travel over the ocean and thus had a limited number of destination and thus limited usefulness. While the technology at the time limited how large it could be and so carried much fewer passengers than sub-sonic airlines could...
The Airbus, etc plane designs are all for maximizing the number of passengers that can be transported at one time and overall that means a lot more people get moved than the Concord could ever manage.
Sure, the Concord could have gotten to and from a destination quicker but if you needed to move the same number of passengers as a much larger aircraft could carry then that speed is negated by the need for multiple trips and could even take longer than the slower aircraft because of it!
While they never stopped developing faster ways to travel... work has continued since Concord to come up with designs that could offer super sonic travel time but try to eliminate the extreme noise of super sonic flight so such a plane could operate over populated areas and thus be much more practical than the Concord, as well as still manage to carry a large number of passengers.
Both the military and NASA as well, working on technology like RAM/SCRAM jets and setting new speed records as they perfect the technology that could one day be used to allow aircrafts to travel anywhere in the world within a hour with near escape velocity speeds.
While the private sector has finally started to get into the space race, something that similarly seemed like a distant possibility back in the 70's, but like this VSHT idea was something that eventually became reality...
So it may finally be time... only thing to still be reserved about is how long before we can catch a ride... It could be well over a decade, or even decades, before we see a viable VSHT network established and servicing most destinations but they have to start somewhere and that's all it really needs to get started... Even the old railroad wasn't built in a day after all...