Even railways from nowhere to nowhere often ended up being useful when the ends were extended to somewhere or when somewhere grew to encompass nowhere.

For example the Berlin Ringbahn was once some billionaire's toy but now it serves very useful traffic, as Berlin grew outwards to where the Ringbahn is.

It is not "often" it is "sometimes" and it is also less than a participation trophy. It does not make the bubble not harmful or even less harmful. It just means that sometimes you can repurpose an expensively build junk.