Yeah, filters only get you so far. Not going to handle salt water for example.

Distilling will do a lot, but still volatile organic compounds with a boiling point around that of water or below will still be present. Would need activated charcoal or something to absorb those.

But I kind of think the straw type filters are for when you are in trouble, and have no choice than to drink whatever (non salt) water is available. That's when it's time for these straws.