Because family members use it and they don't want to use alternative communication methods, because groups you are involved in use it for organization and if yo

Because family members use it and they don't want to use alternative communication methods, because groups you are involved in use it for organization and if you want to stay involved in said groups then you have to use it, because the country you live in has a large amount of its social web woven through facebook. There are lots of reasons. Yes they aren't literal needs as in you are going to die, but sometimes the cost of not using facebook is significantly greater than the cost of using it.