Well you should want to keep them alive as it’s an RPG about surviving in terrible circumstances :) But yeah I suppose you could let them all die and win the game with just your companions but that would feel like a wasted journey to me. IIRC you will get longer at the end of BS3 to finish the final quest if you have a larger caravan though, so yes, there is a direct impact on which ending you get. The game ends regardless at that point, I didn’t complete the final quest but still got a satisfactory ending.
Do you role-play DOOM-guy’s dreams and aspirations too? You know, wife and kids, oldest son’s HS graduation.
That would be stupid!