Ah, but it is mental. It's the game mechanics' effect on your attitude while playing.
You say "I don't want to die because if I do I get punished by the game." That right there is mental: you don't WANT to die.
As far as respawn times go, that's something controlled on a map-by-map basis. Some maps spawn you quickly, others spawn you slowly. It's something that I think should be left up to the mapper so they can determine the pace and flow of their maps.
If the issue is that YOU don't feel that you're punished enough, well, you can always punish yourself instead. Wait out an extra spawn round if it'll make you feel better. But if the issue is that you don't feel OTHER people are punished enough, again, I have to say that this is simply some players wanting to shape the attitudes of other players in the game and change how other players think and feel during the game.
Ask yourself something. Why does it matter how much players are punished by the game for dying? My bet is the answer is "Because it shapes their behavior in game".
I think people who make these claims often want others to be playing more tactically, more cautiously, etc. But I can promise you, no amount of engine change would do this with the players you hate the most. There will always be rambo players in an FPS, or at least that game's equivalent. You think long respawn times will make people more cautious? Consider the +5min "respawn" times of a round of CS:S. If you die in that game, your avatar is dead for the remainder of the round (anywhere from 0 seconds to 6 minutes). And yet, people play that game like lunatics, racing around using "spammy" tactics or whathaveyou.
I remember playing Return to Castle Wolfenstein on servers with One Life to Live enabled. Know what? People still didn't take their virtual lives seriously and would do stupidly brave things that people would NEVER do in real life. And in those games, you had something like a 10 minute round limit so if you died early, you wouldn't "respawn" for another 9 minutes or whathaveyou.
You can't change the way people play. So in the end, excessive punishing of death to the point where people actually FEAR it becomes a fruitless endeavor.
If you disagree with me, fine. I really don't care. People are still gonna complain that there isn't enough fear of death in video games, probably, no matter what I say. I just think that continuing to ask for this or that change, often changes that would be detrimental to the rest of the game either comes from selfish motivations (IE: "I want the game to be more realistic for me, by my definition of realism"), or comes from a fundamental misunderstanding of how other people play games (IE: "Well, I'M careful with my life, so if we did X, Y, and Z, other people would be careful the same way"), and often comes from both places. As such, requests like this are better left for mutators than fundamental changes to vanilla gameplay.