You would imagine sand was abundant, but: https://www.bbc.com/future/article/20191108-why-the-world-is...

Also, glass can be recycled near infinitely and 1 ton of glass created from recycled glass requires 30% less energy than from raw materials: https://www.palpa.fi/juomapakkausten-kierratys/eri-juomapakk...

Also, in another world:

- 87% of recyclable glass bottles are recycled https://www.palpa.fi/juomapakkausten-kierratys/eri-juomapakk...

- 97% of reusable glass bottles are returned for reuse https://www.palpa.fi/juomapakkausten-kierratys/eri-juomapakk...

- Reusable glass bottles are reused on AVERAGE 33 times https://www.ekopullo.fi/fi/

> Most glass is mostly sand, an abundant raw material.

Sand is not actually an abundant raw material [0]. Although sand in general is abundant, sand that is usable for construction and manufacturing is generally found on beaches and flood-plains - desert sand is less angular and usable. We extract 50 billion tonnes of sand per year and this is getting worse as a result of continued massive urbanisation. Ocean dredging for sand has significant ecological input.

This might not be why glass recycling started, but it suggests an incentive for continuing to do so.

[0] https://www.bbc.com/future/article/20191108-why-the-world-is...

AFAIK it's because the initial sand -> glass process is energy intensive, much more so than melting existing glass.

Garbage collectors don't want to handle glass when it's mixed in with the other waste. So it is already collected separately. Might as well recycle it.