I think it depends on the type of the partnership. We die together? You help me die but stay alive? Vice versa?
As Praestat_Mori mentioned, group pressure might be the factor and it goes both ways. Like "we die so you HAVE TO die too" or "one deserts so others also stopped trying".
Personally, i'd love to have someone to hold me and ensure that N2 mask won't come off by accident but atm there's no such person i'd trust that much.