Guy from the 80 said:
Am I alone in thinking health regen is god awful? It removes tactical elements and it prevents you from being punished by bad choices. Games like STALKER where you can bleed to death and has no regen is great, the typical HALO/COD etc ad nauseam not so much.
You're not alone in thinking that, but pure static health with no regen isn't all roses either. I don't really remember looking back on playing through the higher difficulty settings of many older FPS's because all it was was trial and error gameplay.
"Can i go round this corner? Oh, i got shot in the face. Ok, reload, but i didn't see where he was, so i'll have to have a another look. Oh, i got shot in the face again, luckily i managed to see where he was, great. Reload, shoot him, awesome, now i can progr-oh, i got shot in the face, reload.
Shields give you a little bit of leeway in looking round the corner to see where that guy is so you can shoot him, without having to reload the game. Also allows you to have a little fun and take a risk once in a while, knowing you won't have gimped yourself for the entire rest of the level if things don't go strictly to plan.