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Not OP, but same here. Born in the 80s and only our parents have landlines. Though my mobile and office phone receive far more spam calls than real calls. My Google voice line gets a hand full of robot voicemails per day. The "Should I answer?" app blocks a lot, but not all.
Born in the 60s, old enough to be your parent: no landline at our house in I don’t know how many years. We both have a phone that’s nearby all of the time, what would we do with a landline except as a spam vector? And my parents, who are old enough to be your grandparents? Ditched the landline a couple of years ago. I have no idea what the demographics look like for hardlines anymore.
Of the residents I know for sure do or don't have a land line, they are the only ones.