Why is it so important for someone to know that the other person will never leave them?

i think it's just a desire to know that there's always someone there for you...someone there that will always be there backing you up and supporting you and your decisions regardless of if you're right or wrong. it's needing to know that a person can form a relationship and never have to worry about them leaving (taking it for granted? or just seems like it anyway)

Who doesn't want security? Be honest... because everyone does... you want to know that when you buy a home, there a locks... or that when you get a perm, your hair won't fall out... or that when you buy something it has a warranty... those are all forms of security and even though those are materialistic things, those habits carry over in relationships. Most people know words like "always and forever" aren't always and forever, but still... to hear someone say it is sometimes enough...

someone's "need" for something like that is directly related to their self esteem - the less they have, the more the need increases to be reassured.

insecurity- some people are insecure and are so scared that if they love that person will leave them and they will be hurt.