The issue is the way your body normalizes to the new default of higher Serotonin levels - when you suddenly return to normal the present state is worse than the it was before you started taking SSRI's (I read a few good papers on the topic a while ago, but I don't remember their titles now - wikipedia is probably a good place to start: http://en.wikipedia.org/wiki/Antidepressant_discontinuation_...).
Also lack of craving is a ridiculous justification for effectively prescribing substance abuse - for example aderol et. all are amphetamine salts - that people don't have a craving in the sense that they would for cocaine is just because the high lacks the euphoric effect -- they still can't function normally without dosing -- and it definitely doesn't mean it's fucking reasonable to prescribe to seven-year-olds.
Likewise people have cravings to watch their favorite tv-show or check their Facebook accounts - these cravings do not qualify these activities as substance abuse.