About ten years ago I found and ordered a glass bottle with a fitted silicone lid. It’s not tight enough that the bottle can be tipped upside down without the water slowly dripping out, but it’s great for keeping stuff out.
I always wanted to see a company make a glass bottle with silicone top that was completely leak-proof.
I think it’s for anti-tampering purposes. Imagine the consequences if some bad actor tainted those pills with something or replaced the pills with another.
Sheets? For the washing machine? Wouldn’t those require a plastic shell or base like the laundry pods do?