Because transporting it (it's heavy) and recycling it consumes more resources than making it fresh.

Additionally glass is harmless in the environment, and it's not something we can ever run out of.

So why do it?

Additionally, if you actually do want to recycle things, glass shards contaminate everything, making it much more difficult and expensive (i.e. consumes more resources) to do it.

What you're describing is mostly a failure of US commingled recycling system. Meanwhile most of EU countries successfully recycle about 90% of collected glass, collected in glass-only containers.

Making new glass can be an issue, as it typically uses sand, which is not very renewable and sand mining in many countries causes massive issues with flooding, droughts, sinking, black markets, even sand mafia!

No we should not landfill everything after a single use, or we will soon run out of reasonably accessible raw materials in suitable forms.

That's sand for concrete and beaches you are talking about. Sand for glass is not in short supply.

And no, we will never run out of it - the planet is made of it.