Metal straws are dangerous due to for many disabled people due to the risk of injuring themselves by biting down involuntarily because of the same disabilities which necessitate their use of straws in the first place. For many others, the inflexibility of metal straws mean that they do not actually enable them to drink independently.
> Why are people so helpless? Jesus christ, it takes half a second to figure out this solution for yourself.
It is indeed very easy to think of this approach. For people with disabilities which make metal straws unusable or dangerous, it probably doesn't take very long to think of why it isn't a solution for them.
(As a minor aside, as a person lacking any such disability: metal straws can be quite a painful experience with hot beverages. Although I'm given to understand that it's traditional in Argentina with mate, and my Argentine in-laws seemed much more comfortable doing so at a higher temperature than I was, so I guess it is probably possible to get used to that.)