It's a basic and core rule to D&D.
Keep in mind, when you remove that item you're not losing hit points; You're directly losing a portion of your overall health, which is represented by improved hitpoints.
In other words, imagine if someone was giving you an adrenaline drip in real life as the only thing keeping you on your feet, and then they suddenly took that away.
But, no, I agree.
This is clearly a failure with how our medical.. I mean, magical system works. Free constitution care for everyone!
Except for undead. Those punks don't get any constitution.