Certain shapes of sand are rare compared to global construction, sand in general isn't. Unclear what this method needs.

glass is made from sand, there is less glass in world then sand, and again, why lock more precious commodity in another product which we are already making from other less precious commodity ?

It's the shape of the grains of sand that's bad for concrete, not the chemical composition. It gets less angular and more round when it moves in the desert and it doesn't bound well with cement. Sand that is good for concrete is rare and making it is expensive. The "bad" sand that is common everywhere is still perfect to make glass.

twenty-five percent of Africa is literally covered in sand. Sand comes in different granularity and compositions, but for concrete this is often irrelevant.

Uh, for concrete the granularity and composition is VERY important. In fact it's one of the most important parameters you can tweak in a concrete mix.

To the point that weird stuff like this happens quite frequently:

https://www.quora.com/Is-it-true-that-Saudi-Arabia-imports-s...

My local DIY store here in the UK carries some 8 different types of sand, all for different purposes.

Actually it matters quite a bit. That's why countries which are literally filled with desert sand import river/sea sand for their construction. Finding a way to make desert sand usable for construction concrete would be significant.