So am I the only one that has no idea what all the little vials and bottles lying around are for?

Screenshot? So we can understand what are you talking about?

They are health pickups. But they cannot increase your health above 200 (I think that's the limit). There is a super health pickup (looks like a heart) that can make your health 300, but the bottles and vials health pickups cannot be picked up if your health is already over 200. However, the little health pickups that increase your health by +1 can still be picked up, up to the max of 300.

Ah I see! Thanks! So fat I've only played on the easiest difficulty, so I almost never get below 200 health. :)