From a quote by "Claire" in the film Elizabethtown
The significant other of the substitute person
may not "have enough time" or "be too busy" for a relationship, or they
may only be interested for the purpose of sex,
money, status, or general need of someone to talk to during times of stress. The substitute person generally won'
t get the emotional fulfillment from the experience that he/she
may crave, and will feel unimportant yet somehow will continue on out of hope.
This can only end in tears for the substitute person.