High-speed trains are awesome. We absolutely should be building more of them for the people who'd like to use them.

But if someone wants to go directly from point A to B in a "gimmick jet", why should we try to prevent that?

I'll reiterate with your example. Building high-speed trains, and developing "gimmick jets" are not mutually exclusive endeavors. It's clear that you are not personally interested in a "gimmick jet", but there are people who would be. Why exactly should we be stopping those people?