I always tell my best friends, Lottie. You're right about it being a new-ish thing with parents and their kids, though.
My mum can't ever remember her mum and dad telling her and they still don't. My mum tells me that's what made her want to tell us all the time.
Us grandkids always say it to our grandma and grandad, more so now because we know it gets them all flustered when they don't know what to say, but when my grandma was seriously ill about six months ago, she said, "I love you" to us all for the first time. :)