Curate, connect, and discover
We talk so much about why finnick, Johanna, Katniss, mags, beete , wiress, were in the 75th arena, but cashmere and gloss were there for punishment too. I mean it's never stated that they volunteered and they even make statements about their discontent of being there, therefore I do not think neither of them volunteered. I think gloss is there to punish cashmere, a last goodbye from snow to her. Cashmere and gloss come from a career District, so the pool of victors was probably not small, so it would be a very insane coincidence that both siblings were ripped. And if we think about it in every possible scenario one of them would have to see the other die or at least know about the other's death and grieve it (this is if they didn't need to kill each other). And to me this was a punishment from snow, because either she knew to much and had to be dealt with or she refused snow of something and as punishment he sent her and her brother there to hunt her with the fact that would of them would have to die in other for the other to survive, and it wasn't even guaranteed that the surviving sibling being her or gloss would win because of the other tributes.
There is a possibility that Annie volunteered for her games. I saw someone talk about this on tik tok and I thought it was interesting. Annie is from 4, a career District, so there is the possibility of her training her entire life, her volunteering, her going into the games, and her idea of glory quickly shattering once she saw her district colleague be horribly death. she went mad because that's a very traumatic thing to witness, but one thing that might have played into her madness was having this idea of glory being stripped away revealing the reality of the games. After seeing the games in such a romanticised way her entire life, just to realise how ruthless they actually are, destroying her perception of reality. (Since she would have trained her entire life for the games)