[madez]

For what we have learnt from the history of mathematics, you might have to give it some hundred years before people realize usefulness.

As a practical note, the fact that educated people use it is an indicator that it is useful.

[lucozade]

> As a practical note, the fact that educated people use it is an indicator that it is useful.

Possibly. It could also be that they use it because it's interesting and informative rather than useful per se.

It could also be that it's useful in particular contexts in the same way that Feynman diagrams are useful.