Interesting...I never thought of the "anon" programs as encouraging a spouse to stay in a marriage. I think that choice is very personal and individual. The program does help us learn compassion for the addict and to focus on ourselves, but to me compassion doesn't equate with staying in a relationship if one feels she has had enough.
Detachment also can be many things. Some can stay in the front row of addiction and detach from the chaos...others can not and detachment requires physically moving away from that or asking the addict to move. I think Naranon and Alanon help us to understand the disease and our codependency and come closer to detaching with love rather than in anger. But to me none of that means stay if your head and heart say go. The very essence of the program is that it is merely suggested and also that it is focused on our recovery. As such, i don't think doing something that would feel healthy for you...whether that is staying or going...would be in conflict with Alanon.
Perhaps the group you are in just happens to be comprised of spouses who are still in the marriage. My home group has both as well as parents who live with their addicted child and those who have asked them to leave. Hugs