There are 3 aspect to this: need, technology, and capacity.

Hyperloop is basically a maglev, but much smaller, with life support, inside a tube, that must be evacuated from air.

In terms of need, the vacuum tube is not actually needed. We already know you can do 600 Km/h with maglev just fine and with technological advancements you could probably push that to 900 Km/h if you really, really wanted to and the electricity was cheap enough. (this causes goemtric issues with the track but that's another point, and also one hyperloop conveniently does not address)

In terms of technology, pumping a thouosands-Km-long tube to be even a partial vacuum is horrifically hard to do. In addition, the tube creates a bunch of additional hazards.

In terms of capacity, one of the advantages of trains over planes is that because they have a much higher capacity, they can actually do mass transit at scale instead of becoming saturated like airports often are (you know how you take the plane and you randomly have to wait 20 minutes on the taxiway? That). Hyperloop has even less capacity than a plane by comparison. Economics also mean that lower capacity = higher ticket prices.

All this for an even higher cost than maglev (since the tech is maglev with a vacuum tube), which is in turn more expensive still than regular high speed rail.