I kept my landline longer than many, mostly because I used to do radio regularly and cell phones generally aren't awesome for that. But I've been without for over a year. With cell phones they're mostly unnecessary and redundant, but cell phones aren't perfect substitutes. There's something - even something slightly strange in retrospect - about the loud phones jangling throughout the house every time someone calls. There's something about calling a house, rather than a person. It feels a bit weird calling friends who are cohabitating and not being quite sure who to call, as if choosing one over the other is expressing a preference.
Not being a get off my lawn guy here, just observing that ending the landline is actually a change to social norms that had existed for quite some time.