I've rarely (never?) seen a mature player in tears over the death of their character.
I mean it's been a few years since I've seen actual tears but the death of a character hits many players like the death of a pet. The sheer sentimental value of a character that you've kept alive for years of real time and hundreds of hours of play, when you lose that permanently is crushing. It's like having a treasured possession. Sure, you can replace it but it won't be the same. Losing a character hurts, and I'd be totally sympathetic to a player mature or not shedding a few tears the way a guy who had restored an old automobile and then wrecked would. Totally understandable.
I've regularly seen adults in tears when their plans unraveled and the villains achieved their dastardly aims.
And interestingly, I have never seen this at all from any player mature or otherwise. I'm struggling to even understand what the motivation behind the tears would be. This would be like crying that you lost a game of Monopoly? The thing is that no matter how good an NPC is characterized, you never have as much of a relationship with an NPC as you have with your own PC. Sure, I've seen players get attached to NPCS, even seen players get crushes on NPCs, and I've seen players highly motivated to protect or avenge NPCs. But I've never seen the loss of an NPC get a player as invested as the loss of a PC. The closest I've come to that was a player whose PC got pregnant from a relationship who retired her PC because she thought that is what our PC would do, but even that isn't actual tears much less
regular tears.
Regular tears? I mean how many novelists regularly achieve tears from their readers? If that's the case, then you're doing some amazing writing. I know more players that would refuse to engage with a game because it was trying to be a tearjerker and manipulate their emotions than I do ones that would be moved to tears by the death or betrayal of an NPC. When I have NPC's surprising betray the party, the players emotion is more like, "That's so cool. I should have seen that coming. Now let's kill the SOB."
When my old-guard players reminisce about powerful scenes from old games, it's almost invariably about in-fiction losses: death of beloved NPCs, political defeats, betrayals, loss of reputation, etc. Memorable PC deaths do, occasionally, come up, but that's the exception rather than the rule.
When my players reminisce about scenes from old games it's generally about one of two things - amazing victories they pulled off against all odds or else times that they got in over their head and multiple party members died.
Later on another poster talks about the two pre-conditions that he thought must be true for my perspective and that was "new characters are at some disadvantage compared to old characters" and the other was "character driven games". The former is interesting because the "sentimental value" of characters IME means that whether or not new characters are at a significant disadvantage, the loss still hurts. But the second surprised me not because I don't think it was true, but because my assumption was that the further away you get from pawn stance the more important character is for driving the game. One of the reasons loss of character hurts so much more than betrayal or recoverable setbacks like political defeats, loss of reputation, loss of friendship, etc. is that losing all the character's story that you wanted to tell hurts far more than just losing the particular story you had in mind. If the story of your PC twists in a way you didn't expect or even want, well there is at least a story and a least a path forward even if it's not your first choice. But if you lose your PC in some permanent way - death, disfigurement, maiming, etc. - well then that story is over, and that hurts more than going down path B instead of path A.
I will say this. If that's not remotely true of your game, then I'd love to sit in on it and see how you manage it.