Paper straws break down relatively quickly and can lose suction effectiveness as a result. Reusable metal straws can cause chipped teeth or gum damage if bitten down on by someone with poor fine motor control. No straws at all can leave an individual unable to ingest liquids entirely. Reusable soft plastic straws would be ideal, but the tradeoff is that now we've placed yet an extra burden on an impaired person (or their caretakers) in our society because now they'll need to maintain a supply of clean, reusable straws that they need to transport with them. Disposable plastic straws are "soft" enough to not damage someone's teeth or gums too severely when bitten down on, but are more durable than paper straws to ensure reliable suction over time, and they do not require any upkeep or maintenance for proper hygiene due to their disposable nature.