I've been given a metal straw at a restaurant. My immediate thought: how do I know this is clean on the inside? I can't see in there, it could be full of mold. I just drank from the glass instead, because I'm an able-bodied adult.

Many commercial dishwashers might be specialized for certain dishes, so adding a straw washing machine would be a significant expense. In addition, I've heard that many commercial dishwashers require the dishes to be scrubbed beforehand (see https://www.webstaurantstore.com/guide/620/types-of-commerci...), and straws are quite difficult to scrub.

Given that most restaurants that go through a lot of straws want to provide the option for takeout anyway (for which you can't use metal straws), it makes sense that most restaurants don't bother.

Don't a lot of restaurants just employ dish washers and not use commercial dishwashers? They are super fast and easy to clean with a brush designed for them

I have a friend that owns a cafe. They tried metal straws for exactly the reasons you outline.

Problem was: they're expensive and people steal them!

Solution? Exploding metal straws

Seems like it would add to the cost, but I'm behind this on general principle!

Why not straws made out of recycled paper/cardboard?