Because, dammit, I want at least ONE of my DA pairings to have children. Alistair and Mahariel can't have because of the taint, and my Hawke is stuck in the Fade (and I don't think she and Anders would be having kids while they're on the run). 
Same here. I'd like at least one of my female characters having children and a family. 
I wanted this for my Nareth Tabris, she have very motherly instinct. (I always picture her as the more mature of the tree cousins, and she was the one who protected Soris and Shianni. I always loved the idea of the tree being childred together) But BioWare had to broke my headcanon of her and Alistair leaving the Warden to adopt some elven kids and living happily in a remote villge where nobody knew who they were.
but no. BioWare have to always take out the Warden and never let her/him go. Really, people would not ask so much of the Warden if BioWare didn't tease so much about her/his phate!
Hawke I never had much interest in. Maybe the only one I have saved and is with Fenris, but all the others (actualy I played to colpetion only two) I'm glad I could let them die. 
Shepard I would have loved for her the house at the sea with her little baby Krogan adopted with Garrus. But than the tecnicolor ending and stupid Casper came... 
At least in Inquisition, I'd like a character with a happy ending. 