i can understand group #1
they were just waiting out their husband's 2 year bid or whatever
group #3 is
status - serial killer groupies, drama queens, etc
they only "date" inmates
and actively seek to do conjugal visits with prisoners, wanting to have their children
personally i found group #2 to be heartbreaking
story after story of being used up and discarded
basically a woman is going through life minding her own business
then she gets a letter in the mail-
"hey, we used to be classmates in 6th grade, remember me??
welp i'm locked up for a crime i didn't commit
i'm so lonely
please write to say hello if you have time"
so she writes back because..why not??
then she checks with his mom "oh my baby is innocent"
then before long she's putting $10 on commissary and driving 3 hrs to visit him
accepting a marriage proposal
supporting (emotionally and financially) his quixotic path through the correctional system
then she gets dumped the second he is paroled,
or worse- he stays with her long enough for her to realize his true nature
that he's not so sweet and even-tempered when he's been drinking
or doesn't have c.o's to keep him in line