Regenerating health and implicit meters

Here’s something I haven’t figured out yet - why do regenerating health and implicit health meters always go hand in hand?

Back in the day, it was normal for most or all games with health to show explicit health meters, whether it be as a number (as in, say, the original Doom), a numeric visual representation (as in, say, The Legend of Zelda’s heart containers), or an analog display (as in, say, Street Fighter II’s health bars). It was also normal for health not to regenerate over time but to require pickups if it was possible to restore at all.

Then we got Halo and Gears of War and stuff and it became common for shooters to have regenerating health and also implicit health meters, generally via making parts of the screen increasingly bloody or dirtied and eventually turning the visuals black and white and dulling the audio. It seems like these always go together - I can’t think of a game with quick health regeneration and explicit health meters, or a game with implicit health meters and no health regeneration.

Why is this? The speculation I have is that in games without health regeneration, health is a resource to manage (do you shoot the enemy from afar and spend more of your limited ammo or charge in for a melee kill at the cost of some health as they attack back, etc.) and thus it’s important to know exactly how much of each resource you have left. Whereas if there is health regeneration, then what’s important to know is whether you are currently in danger, and if so, how much.

What bothers me about this is that, due in large part to how inconsistent the iconography is across games, it’s often difficult to actually understand how much danger you’re in with an implicit meter. This troubled me a lot in Just Cause 3, where the screen gets bloody and then goes black and white as you take damage. But there’s very little readable granularity during the ‘bloody’ phase - I’ve just either taken some damage but not enough to worry about (bloody screen) or I’ve taken a lot of damage and I should run away (black and white screen), without much in between or a good way to tell how quickly I’m taking damage. The result is that I often feel like I’m going along fine until I suddenly get overwhelmed out of nowhere and die, when in reality I was probably in serious danger for a while but didn’t realize it.

I can’t help but feel like a health bar would avoid this problem - I’d always be able to see how much buffer I have and how quickly it’s depleting. Why can’t I have health regeneration and a health bar?