Price performance. If the failure mode is slow, then my sport (rowing) could love this for cheaper boat construction which is stronger than fibreglass but cheaper than carbon fibre. I imagine surfboards and kayaks could work too.

Being flexible and non conducting is useful.

In addition to what sibling posts say, basalt is certainly abundant. Per Wikipedia, 90% of volcanic rock on earth is basalt. We're not going to run out of it.

See uses here: https://en.wikipedia.org/wiki/Basalt_fiber I am no material scientist, so cannot comment on actual facts why it might be better in specific cases than Kevlar, Dyneema or Carbon. But from experience there's a lot I don't know and especially in engineering there's a lot to consider when putting materials under stressful conditions that might put this in in a specific spot superior to those mentioned above.

I can imagine (I have no clue about this, I just watch manufacturing videos) that this is easier to mass produce. A less refined version of this is used to make Rockwool, an insulation material similar to fiber glass. Melt the stuff, extrude it, ????, profit. https://www.youtube.com/watch?v=t6FWPTZjwLo

All those burn.

Basalt does not burn, so its main competition is glass fiber, not organic fibers.

Also, those 3 mentioned by you are currently quite expensive in comparison with other fibers.

I suppose because basalt cannot be patented. Or at least cannot be patented outside the US.

Say, is Carbon in your statement a trademark?

It seems to be more heat resistant?